Using Magic 's recent Commander Brackets model for ranking decks, I'll tell you where the Final Fantasy decks fall, and what levels they can likely compete against
If your deck is built around lands, like Omnath, Locus of Creation, focus on land-based ramp
Heliod is simple, whenever you gain life, you put a +1/+1 counter on a creature or an enchantment you control
This is partially thanks to how well the cheap creatures available synergise with your big-spell theme, and partially thanks to how the mediocre removal hurts your chances of going long against green ramp players
The extra draws make opponents less mad when their best spell gets countered
Answer: There are a few things you can do to increase your chances of pulling a rare card in Lorcana The First Chapter: Buy more booster packs