When I was theorycrafting this deck I wanted to make a mill deck with no creatures that relied on Sphinx's Tutelage to mill, and an excess of control to deal with any situation your opponent may throw at you. In the end there were a handfull of creature cards that I felt gave more depth to the control this deck exerts. I have only played around 30 hours of Origins so far and have had around a 75% success rate with it in multiplayer.
1x Disciple of the Ring
4x Bone to Ash
3x Sphinx's Tutelage
3x Fleshbag Marauder
3x Calculated Dismissal
4x Reave Soul
4x Twin Bolt
4x Fiery Impulse
2x Drowned Catacomb
2x Sulfur Falls
2x Dragonskull Summit
2x Dimir Guildgate
1x Rakdos Guildgate
The early game is fairly critical to this deck. It does not require much setup but getting one of each color land can be an issue early, as well as getting 2 islands for the later counters. The key early game tactic is controlling the opponent until you can get the Sphinx's Tutelage out and mill them down.
Idealy you never want to allow your oponent to have more than one creature card out at a time. By doing this, if they play something so large that you can not burn it down with spells, or counter it due to lack of mana, you can force them to sacrifice it by using a Fleshbag Marauder. The Fleshbags are great for stopping large creatures, anything with Hexproof, or Gaea's Revenge which cannot be countered and posed a problem to this deck before their addition.
At 4 land (or 3 with Calculated Dismissal) you gain more control options as this deck contains 11 counterspells: 4 for creatures only, and 7 for all spells. Managing your land so as you can counter any gamechanging cards your opponent may play is a large part of the tactic at this point and will only come with experience. Idealy by this point you have gotten one of the 3 Sphinx's Tutelage and you can start to turn up the milling by using inspiration when you have excess land, as well as the ability to draw and discard on the Sphinx's Tutelage itself.
The two Disperse were added for the odd occasion when a large creature gets played and I don't have the land to counter it. I can then send it back to the opponents hand and make sure I keep the mana to counter it next turn. Disperse is also great for the Aura decks, which from my experience seem pretty common, and strong. When they pump a creature up with multiple aura you can return it to their hand and send the aura to the graveyard.
The majority of the rest of the cards are direct damage spells or indirect damage spells which also effect creatures with hexproof. These spells are can be used to clear out the weaker creatures to keep the pressure off you early in the game and leave the option open to fleshbag or counter anything significant your opponent plays. If all else fails you can try to combo multiple damage spells to take out large creatures once you get into the mid or late game, if they manage to get through your defences.
Finally, Disciple of the Ring is the only creature in the deck intended to stay on the board. I added it for the synergy it has with this deck as there are always lots of instants and sorceries in your graveyard. You can either use it to tap creatures at the start of the opponents turn so they cannot attack with them; or you can use her to counter any non creature spell unless it's owner pays 2 land. These abilities can be used multiple times as long as you have spells in your graveyard to discard.