Can you choose your faction in Dragonfire?

Choosing your faction isn't guaranteed. The game's first goal is to balance the 3 sides, so even if you state a preference, you can be placed in another faction to avoid creating an imbalance.

What you need to understand:

• Balancing comes before individual preference (otherwise everyone would pick the same side).
• Your faction changes every season: don't get attached to one side.
• If you want to play with your friends, the right lever is not the faction but the Alliance — that's what keeps you grouped reign after reign.

There is one option for placement: the Mercenary, which assigns you a random faction in exchange for gold. It's not a way to pick your side (quite the opposite, it's random), it's a way to get placed while earning a reward. To stay with your group, bet on the alliance, not the faction.