That's a hard question to answer. It's completely up to the GM which player's will get into their games. Some GM's may respond right away, while other's may wait to see what kind of response they get from their game listing. Some may want more pre-game correspondence to better understand expectations, experience, availability, etc. Keep in mind GM's may have real-life obligations that limit their time on roll20. Player's out number GM's substantially, so it's best to just be patient. Good luck.