Being a two-colour aggro strategy makes this deck a little difficult to mulligan with. You are looking for an opening hand with both colours and a soul sister. If you have to keep a one colour hand, white is most needed early and green can come later.

Soul sisters are your early game keeping you alive against the faster aggro decks and burn. Then come the toughness boosting creatures and enchantments which allow you to make combat difficult for your opponent. Pallid Mycoderm is the finisher, if your opponent can't deal with it he will eventually take over the game for you.

Getting the most out of the soul sisters and Midnight Guard is important and sometimes requires playing lands at the end of turn after attacking (pseudo vigilance) or using an instant at an odd time gaining you just enough life to survive another turn. Just pay attention to what you have on the field and the potential triggers available.

If the standard aggro plan doesn't get you there look for an opportunity to go for the combo finish in Midnight Guard + Presence of Gond. This is a somewhat slow combo because you need to wait a turn to untap Midnight Guard and be able to go off. On the other hand it's stable, even if they can deal with your token army for one turn (e.g., Electrickery) you can just repeat the combo next turn. With a soul sister the combo is also for "infinite" life. One thing your opponent might try is to interrupt your attempt to combo with instant speed removal. If you have and instant speed token generator (Sprout Swarm, Scatter, Evangel) you can create another token, untap Midnight Guard, and continue on with the combo with removal on the stack.

Final thought, don't get stuck with the idea that you have to save Presence of Gond until you draw Midnight Guard. Often that is the correct play but sometimes you need those extra tokens to gain a bit of life, to set up convoke, or just to generate a chump blocker. This is not a pure combo deck where you have to assemble the combo at all costs. It's really a soul sister aggro deck with a combo built in if you happen to draw both pieces. 

Delver Fae
-4 Selesnya Evangel, -1 Pallid Mycoderm, -2 Scatter the Seeds | +4 Scattershot Archer, +3 Sunlance

MBC
-3 Selesnya Evangel | +3 Sunlance

Burn
No sideboarding

Kuldotha Boros
-2 Selesnya Evangel, -1 Pallid Mycoderm, -1 Scatter the Seeds | +4 Gleeful Sabotage

RUG Tron
-2 Soul Warden | +2 Gleeful Sabotage

Dimir Teachings
No sideboarding.

Eye Candy
-4 Selesnya Evangel, -3 Scatter the Seeds | +4 Standard Bearer, +3 Sunlance

Counterburn
-2 Selesnya Evangel,  -2 Pallid Mycoderm | +4 Scattershot Archer

Affinity
-4 Selesnya Evangel, -1 Pallid Mycoderm, -3 Scatter the Seeds | +4 Gleeful Sabotage, +3 Sunlance

White Warriors
-2 Selesnya Evangel | +2 Gleeful Sabotage

Goblins
-2 Pallid Mycoderm, -1 Scatter the Seeds | +3 Sunlance

Elf Bomb
-3 Spidersilk Armor | +3 Sunlance

Infect
-1 Selesnya Evangel, -3 Spidersilk Armor, -3 Scatter the Seeds | +4 Standard Bearer, +3 Sunlance

Domain Zoo
+4 Scattershot Archer +4 Gleeful Sabotage +3 Sunlance

RDW
+3 Sunlance

Hexproof Auras
-4 Veteran Armorer, -3 Spidersilk Armor | +3 Gleeful Sabotage, +4 Standard Bearer

Stompy
-1 Selesnya Evangel, -2 Pallid Mycoderm | +3 Standard Bearer

Suicide Black
-3 Spidersilk Armor | +3 Sunlance