Do you have to pay to be good at Game of Thrones: Dragonfire?

No, paying isn't required to be good. Dragonfire is a game where strategy (army affinities, Order↔Habit synergies, which star tiers you chase) weighs at least as much as your wallet.

What money speeds up:

• Comfort (the Lifetime Third Builder = faster build queues)
• Progression speed (Cores to level Habits, Relics for stars)
• A few one-off jumps (an instant Star Rank on a dragon)

What money doesn't buy: a good army composition, respect for the cavalry/archer/spearman triangle, or the right matchup in a fight. A free-to-play player who plays sharply regularly beats a spender who stacks badly. Money buys time, not judgment.