Golgari Proliferation. Ramp mana, put counters on planeswalkers and sagas and win the game.

Lands:
8 Forest 
5 Swamp
4 Overgrown Tomb
4 Woodland Cemetery
1 Karn's Bastion - Proliferate on a stick for desperate times. Maybe add a 2nd?
2 Blast Zone - Proliferate can turn this into a full-fledged board wipe very fast. Just dont hit your own planeswalkers..

1 Planewide Celebration - Your "ultimate". Very versatile. Put counters on planeswalkers, get stuff back from the grave, create blockers or gain life
3 Evolution Sage - Lightning rod, try to play this and then a land afterwards. You can play Blast Zone and directly add another counter. Combos with Mending of Dominara.
4 Pollenbright Druid - Either put a counter on Incubation Druid (ramp) or Leyline Prowler (defense), or proliferate. And you get a blocker that you can sacrifice with Vraska, Golgari Queen or Liliana, Dreadhorde General.
2 Vivien Reid - Very strong green planeswalker. Searching for lands works well with Evolution Sage and the ultimate ends the game.
2 The Mending of Dominaria - Combo piece together with Evolution Sage. Play this, get back a Pollenbright Druid, play a land (->proliferate), play the Pollenbright Druid (->proliferate), Mending triggers, Evolution Sage triggers some more times and you should have gotten at least 2-3 counters on a planeswalker, winning the game.
2 Liliana, Dreadhorde General - Very strong new planeswalker. Creates blockers, draws cards and has a strong ultimate.
2 Vraska, Golgari Queen - Sacrifice lands before triggering Mending of Dominara, Destroy enemy 3 creatures/planeswalkers/enchantments and has a ultimate that can win the game.
2 The Eldest Reborn - Another saga that can be fulfilled in a single turn.
3 Assassin's Trophy - Extremely versatile removal against anything that threatens your combos.
1 Find // Finality - Get back your creatures or wipe the board.
3 Leyline Prowler - Strong anti-aggro card that also ramps. Very strong with some +1/+1 counters placed on it.
4 Llanowar Elves - Ramp.
3 Incubation Druid - Ramp druid and lightning rod. You can put a counter on it with Pollenbright Druid.
4 Treasure Map // Treasure Cove - Card draw and more mana. With proliferation you can trigger this in two turns.

Sideboard:

1 Crushing Canopy - Against enchantments and flyers.
4 Duress - Against control.
1 The Eldest Reborn - Against planeswalkers.
2 Davriel, Rogue Shadowmage - Against control and midrange
1 Arguel's Blood Fast // Temple of Aclazotz - Against discard
1 Phyrexian Scriptures - Against graveyard decks
2 Cry of the Carnarium - Against aggro
1 Find//Finality - Against aggro and board wipes
1 Casualties of War - Against planeswalker decks
1 Leyline Prowler - Against aggro

Tricks:

Pollenbright Druid can put a counter on Incubation Droid.

Proliferate can add counters on sagas, Blast Zone and Treasure Map.

Evolution Sage and Mending of Dominaria go well together.