Hello fellow clashers, my name is Charizzle. I've seen quite a few threads asking about upgrade priority, so I decided to start my own little "guide" on it. I will be going over in detail, defensive and offensive upgrades, and what makes them more or less important than other upgrades.
Ok, now on to the actual guide. I will go over defenses, traps, offensive buildings, offensive troops/spells, and resource buildings, saying what I believe it the most important to upgrade, or if you are a freshly upgraded new town hall whatever, which new stuff you should focus on. Keep in mind that this follows my gameplay perspective, so if you do now share that perspective you may disagree with some points. My gameplay revolves around resources over all. I love war, but I will always upgrade something that protects and helps me get resources easier. After all, loot is the lifeblood of this game, without it there is no progression.
Now I think that offense should always be prioritized over defense, from a farming and a war perspective. First I will go over the buildings that help your offense.
New hero if one is available: Th7s, focus on that king. Its hard, and will take some time, because you cant collect dark elixir to use right when you upgrade to th7, but still try and get him ASAP. Th8s, save 40k DE while upgrading to th9, so that you can buy her as soon as the upgrade finishes.
Spell factory: This should be your top priority to upgrade when starting a new town hall level (if you have an upgrade available of course.) Having a new third spell, or fourth, or fifth, adds so much more power to your attacks than if you didn't have that extra spell, also, having a new spell unlocked can change the game for your attacks.
Lab: I don't like saying this should be your #2 priority. It really should be #1 along with the spell factory. Try and upgrade the lab and factory together if you can. The quicker you upgrade your spell factory, the quicker you can upgrade your troops to whatever new level you unlocked.
Barracks/Dark Barracks: Upgrade at least one of these to the max you can get as soon as you can so you have the new troop available.
Clan Castle: I'd honestly rank army camps higher than CC for top priorities, but since this uses gold, and you can upgrade it without having to fight over what deserves your elixir, I thought I'd put it with the spell factory and lab. Upgrade this with gold while your spell factory and lab suck up your elixir. This is one of the few things in the game that help your offense and defense, so its pretty dang important. If you are a new th9, prioritize this even more. 30 troop space lets you hold the two highest housing troops in the game, and with it, you can now request anything.
Camps: Next on the list is army camps. More troops = better chance at 3 star. Simple as that.
Dark Spell factory: The newest addition of clash of clans. Even though this building is important to have, I put it so low because there are other things that need elixir starting off that it can be hard to squeeze this in. I'd suggest doing this while you are upgrading your camps.
Next is troops. I will be listing what troops you should focus on upgrading in the lab first. Also, I won't be considering heroes as being troops, because they don't use the lab. I will however talk about spells as well because they use the lab. Since there are different troops that have different degrees of usefulness at each Town Hall level, I will go by town hall levels starting with town hall 6 for this section. I will stop at th9, because I am not a th10 and don't fell like I should be giving advice on it. If I don't list a troop/spell it means that you should save it for last.
All town hall levels
Farming troops: Primarily the barbarians, archers, and giants. At th9, giants to level 6 is especially important. If you are of the war above all mentality, you may disagree, but getting your money makers upgraded will help you in the long run to upgrade stuff for wars.
Wizards: Wizards are useful to have maxed at all town hall levels. They are used in many strategies either as the primary damage dealer, or the funneler. They have the highest dps per housing space of any troop in the game. They are important to max out.
Giants: Pay special attention to giants at this level. Giant/healer is one of the most powerful war strategies for th6. Wizards are a key part of this strategy as well, but they are a priority for all town hall levels so you should be planning on upgrading them right away anyway.
Healer: Again, giant/healer is extremely effective at th6, and healers are the backbone of that army.
Heal spell: Useful for war and farming. Giants under one of these babies will be nigh unstoppable.
Wallbreakers: Helps the giants get into the base on giant/healer. Very helpful.
Balloons: Balloons are another useful war troop at th6. With only one AD, there is little that can stop them.
Goblins: Goblins can be useful in farming. They target resources exclusively, so adding a few to your barch can help nab some extra loot that your archers weren't quite able to get.
Lightning spell: Since you can only have 2 of them, they don't have much of a use at th6. Save these for last.
Dragons: These guys are the terrors of th7. Virtually guaranteed to 3 star another th7 in war if you have three lightnings as well.
Lightning spell: This spell becomes extremely useful now at th7. Assuming you upgraded your spell factory, you can now hold three, and can completely destroy an AD with those 3 spells. I don't exactly remember the math, but I think you need level 3 lightning to take out level 5 AD. So get to it.
Rage spell/healing spell: With drags and zaps being the go-to strat at th7, you may not find too much of a use for these spells. But you should upgrade them nonetheless. It can help with farming to give your troops a little boost, and 1 heal 2 rage can be an effective alternative to 3 zaps while using mass drags (but I still highly recommend 3 zaps).
Minions: These help with farming a lot. but shouldn't be top priority because barch is effective enough at th7. Still, get them when you can.
Hogs. Level 2, the max hog level for th7, isn't that useful, at least not compared to mass drags, so don't prioritize it. Still do them before moving on to th8, because you will be one step closer to level 4s, which wreck at th8.
Hogs: Level 4 hogs absolutely demolish at th8. Get them maxed ASAP and you will be a force to be reckoned with.
Golems: Extremely important troops for the last three town hall levels.
Heal/Rage spell: With hogs being a major powerhouse in th8, you should upgrade their favorite spell, the heal spell, as well. Rage helps immensely with gowipe, so get that upgraded as well.
Pekkas: Gowipe is a powerful th8 war attack. Having high level pekkas will help that attack a lot. You get 2 additional levels of pekkas at th8, and level 3s are very powerful.
Valkyries: They are often overlooked, but at th8 they can be a major powerhouse if you use them well.
Wallbreakers: They are useful for gowipe and similar strategies to get your troops in the base.
Dragons: A powerful troop in early th8, but late th8 they start losing their luster.
Balloons: Dragloon is a powerful war strategy at early th8, plus, having balloons at level 5 will mean you can upgrade them to level 6 right away when you hit th9.
Minions: th8 is when BAM gets very useful IMO.
Poison: I actually don't know if you can upgrade a poison spell at th8, because I got my dark spell factory at th9. If it can, don't make it a priority because level 1 poisons are plenty powerful.
Giants: I know I put this for all town hall levels, but they are especially critical for th9. Level 6 giants are beasts for farming. They are one of the most important troops to upgrade for th9.
Balloons: Another troop that gets a huge boost for leveling it from 5 to 6. The power of the black balls of death is immense, which is why this should be the first war troop you upgrade for th9.
Hogs: Hogs are one of the most powerful attack strategies at th9 when you max them out. Buffing giant bombs still can't stop dedicated hoggers from finding ways to wreck bases with hogs.
Golems: Golems are critical for many th9 attacks. Many th9 strategies use two phases, the first being a golem based killsquad. Getting these tanks maxed will protect your killsquad longer, making them cause even more havoc on the first phase.
Heal/Rage: Heals are the primary spell for hogs, and rage is the primary spell for lavaloon, both of which are some of the most powerful attacks at th9. They are both equally important.
Witches: Witches are very versatile. Gowiwi is a decent th9 war attack. They are also used for cc killing, cleanup, and killsquads. Plus, you only need to upgrade them once to be maxed.
Lava Hounds: The extra health is nice, but what really makes these great to upgrade is the extra pups that spawn then it dies. They can make the difference in a lavaloon attack.
Jump spell: A level 2 jump has twice the longevity of a level 1, and that can be huge when trying to funnel your troops in.
Valkyries: Maxed valks are very powerful at th9, making valk strats a force to be reckoned with at th9.
Minions: With giants level 6, BAM kinda falls off the radar, but they can still be used for farming, funneling in war, and cleanup.
Haste Spell: Im currently upgrading mine to level 2 and haven't used them at all yet, but I've heard that they can be powerful for lavaloon when upgraded.
You should put your offensive building before these in every case, except for building a new drill when it comes along.
Collectors: Free loot! Yay! Prioritize your drills bfore your mines and pumps. Prioritize building new collectors before new defenses.
Storages:Build the new gold and elixir storages right when you upgrade town halls. They take like a minute each, and you can start working them into your base design. Don't worry about upgrading them until your offensive buildings are maxed. The DE storage should be built right away at th7, and you should max it before moving to the next town hall.
This may be the section with the most disagreements, because many people have a different idea on what defenses are the most important. Remember that this guide is from a loot protection point of view. If you are a war only guy, you may disagree. Also, defenses should always be prioritized below offense. I will be including heroes because upgrading them requires a builder.
Extra defenses: By extra I mean the defenses that you already have but unlocked an additional one at whatever town hall level. Archer towers, cannons, etc. I do NOT mean the defenses that are introduced at a later town hall level like xbows and infernos. You should build the extra defense, and upgrade them to match the same level as all your others. That should be your first priority.
Heroes: You don't have to max these out while completely ignoring defenses, but you should have a least one upgrading along with your defenses at all times.
Mortars: From a loot protection perspective, this is the most important defense to max. Barbs and archers, the most common farming troops, get shrecked by mortars. For the war above all type player, mortars might not appeal, because they aren't as effective in war. They also have a great intimidation factor. I always stay away from bases with maxed mortars when I barch.
Teslas: These guys are great for farming an war. They are a little lackluster at low levels, but they quickly become some of the highest damaging defenses when you upgrade them to high levels.
Air Defenses: Ignoring these will make you a laughing stock to dragon and lavaloon users. Maxing them out however will make them think twice about attacking you, and they will be a thorn in any air attack's side when you do get attacked.
Wizard Towers: Their damage may not be the best, but they can attack ground or air, and deal spash damage, making goblins and minions alike tremble in terror.
Xbows/Inferno towers: For the war above all player, these wouid be lowest priority. But they can help with loot protection immensely.
Giant Bombs: The Hog Rider's worst nightmare, and bacon lovers dream come true. Yes, these are primarily made for hog defense, but can be great for farming too when an unexpected barbarian walks over it and it blows up half of the attacking army.
Seeking Air Mines: Bane to dragons and Lava Hounds everywhere. Extremely important for wars.
Air Bombs: I can't tell you how many times I've been BAM'd, and someone deploys a wall of minions headed straight for my DE storage, but an air bomb comes in to save the day by blowing most of them sky high. Seriosuly, they are the giant bombs of the sky.
Archer Tower: Long range plus the ability to attack air units makes these very useful for war, however because they are a point defense they aren't as helpful in loot protection. They are great at hero killing though.
Air Sweeper: Even though it is easily dealt with if you know what you are doing, the inexperienced clasher can have a lot of trouble dealing with the hair dryer.
Cannons: They are like an archer tower that can't attack air troops. Good against high health war troops if nothing is shooting at them, but not terribly useful in loot protection.
Skeleton Traps: Nice for a distraction, and the more skeletons the better. Also great at hastling hogs or balloons while they go for defenses.
Walls: Now, walls are important, don't get me wrong, but the reason I put them so low is because of the added war weight to them. Don't ignore them, but also, make sure that you prioritize defensive upgrades a little bit more than walls.
Bombs: These aren't that special. The damage is minimal, the blast radius isn't that big, and they increase trap re-arm cost for little benefit. Useful if a group of archers walks over a cluster, but a mortar will probably deal with them first. Don't completely ignore them, but save these for last.
Well that concludes my complete guide on upgrade priorites for defense, offense, and resourse buildings. I hope you enjoyed it and I hope I was able to help some people out. Happy Clashing!
Source: Charizzle's guide to upgrade priority- http://forum.supercell.net/showthread.php/793232-Charizzle-s-guide-to-upgrade-priority