Your deck is as good as the decks around you. Geth is a highly oppressive commander that can utilize your opponents decks against them through incredible reanimation ability. Not only does his ability not cause him to tap, so it can be used more than once a turn, not only is it able to grab not just creatures but artifacts as well, it is also self fueling which make it very easy to go through your opponents entire deck. The trick is knowing what to bring back, when to bring it back (since the ability can be used at instant speed) and how to utilize what you bring back in the most efficient way. In addition, knowing how to spread out your reanimations over multiple opponents can be tricky but this deck can be very hard to beat once it gets a foot hold.

The basic plan here is build up your mana. You'll want to be tutoring up one of the many mana execrators to put you into your later game as soon as possible to ruin your opponents strategies with multiple board wipes into reanimation or mass hand discard (depending on what you search up). Given the right hand however you can set up a quicker reanimator play with Buried alive to also cripple their early game.

If you didn't have a good early game, this becomes about reseting the game as best you can through field wipes. You'll want to get any many creatures in the graveyard as you can for the late game so you have plenty of options to work with. 

This is where this deck truly shines. It can generate massive amounts of mana to fuel either Geth or to pump into Torment of Hailfire or Exsanguinate for lethal results. The original point of this deck was to be mono black mill though, so don't be afraid to mill your opponents out. The addition of Bloodcheif ascension and mind crank was recent, but along with Geth they are by far the two best cards in the deck, not even needing the other to work well for the over all strategy. Though it must be stated there is no way to get back Bloodcheif ascension so be carful when you play it. That being said, mill is not your only option. filling your opponents graveyards and stealing their creatures can result in a win all by itself.

There are some very good targets for Geth that can lead to quick wins. My favorites are Cloud of feries and other cards like it along with a sack outlet such as Phyrexian Tower, which can quickly mill out one or more oponents depending if you have other things like Cabal Coffers or Nykthos up. The real beauty of this deck is flexibility. Geth being able to steal creatures opens up a whole plethora of combinations that may only become apparent once you sit down and start playing with other people. Be it something simple like reanimating Seedborne Muse, or more complicated like your opponent's kiki combo (maybe even from two different players). This is NOT a casual deck, and I need to stress that. I am currently bared in my play group from playing this deck as it tends to run away with the game with in a very short span of time.