How much do you have to spend?
If you arent too fussed about buying new and your on a budget, then I would look at 2nd hand. You’ll get a good one for £300.
If your relatively tall then go for one with a 21inch top tube and get some high rise (8inch) bars aswell.
The thing to remember with bmx’s is small adjustments make a massive difference. I could probably ride any of my mates mtb’s down the same trails I do on mine. But with bmx I struggle to ride my friends bikes because they all feel completely different yet they all look relatively the same to the untrained eye.