Commission, conditions for depositing and withdrawing funds, responsiveness of the support service, honestly, reliability. This is what you need to pay attention to.
Consider things like the broker’s trading platforms, regulations, commissions, and spreads in the beginning. Like it’s important to use a low spreads broker like fxview or pepperstone to save up on the trading cost.
I like Oanda, even though I had a major problem with them in the past. They are not as good as they where before they were bought out, but in the US we are limited.