If you are limited on gems and F2P like most, Phoenix Rising is like the best pack to complete. You should go for a Phoenix Deck and finish Naturia. I think Genex is decent too. Phoenix is Tier 1 and Nat is really good on budget
Wtf.. Someone recommend a naturia? Come on, we don't need more pollution. There are so many decks out there, why naturia? The game is not about just winning but also about learning to build deck and skilled playing. I would say start with spell casters, its not the strongest but it can work out to be something with other combination. Its creativity that makes one learn.