Hearthpwn

Good Tech cards

Elise the Trailblazer

White Eyes

Good when against control. Generally would cut volcano or Tol'vir for either of these cards, or both.

Stone Sentinel

Good against aggro. Switch out Blaze Caller for this depending if you are facing agro or control/midrange

Devolve

Good for aggro. Cut a hex or mana tide

Game Plan:

early game: you want to mulligan for jade claws and maelstrom portal. Despite firefly being a one drop, you often want to hold it until you know you are going to play an elemental synergy card, or if you are in the top decking phase and might top deck one. Totem often, and don't be afraid to play a naked mana tide totem, as it is a sudo taunt.

Once you make it through the early game with board clears and totems, you should begin to develop your board and try to stabilize with your healing. Use Flametongue totem to use your other totems to get value trades and develop cheap things from below. It is in this phase where fire fly is at it's strongest as often you have extra mana, and have not played an elemental yet to set up future turns.

Depending on situation, use servant of kalimos to obtain late game value cards, or use it to find more stabilization cards to whether aggro. Against aggro, you often want to make them concede by punishing their extension on board. Against midrange you want to out value them, and keep a full hand with mana tide. You can develop strong boards pretty easily with your flametongue totems and thing from below as mentioned before. Against control, unless it is quest priest or warrior, you can fatigue them. Against quest priest and control warrior you want to develop your board early, and try to apply pressure to them.