I don't know much playtime exactly, but I'd say like a month or two month or so should do it.
Usually from what I've seen on the forums, most applicants that have a short playtime, usually a few days, are declined to various reasons, that being one of them.
You do want to be involved with the community though, make sure your rep is good, clear any old chatlogs and by that I mean that you should make a new person out of yourself if you have a bad past with anything in the chat.
I hope the best if you're applying, have fun on the servers, discord, and forums! It's a nice place here, SnakeVirus.