Well you have no idea who you are comming up against so it's a gamble.. There are a few skill based games here in gambling, which forum whould I post in? Did you even read my post about different stakes? $1 buyin, $5 buyin etc, you buyin where you feel safe - the leveling system could make it impossible for good players to buyin at $1.
PVP is a nice idea but it just wont work.
Having user levels and matching players for games based on that won't matter, people who are using bots will just create new accounts so they can play against new users.
There isn't a way to prevent this beside getting into an arms race which is ultimately futile.
The only way to make this work is as bitbaby suggested.
make it sort of like a slot game, you push in a quarter and play and win rewards by clearing levels.
But then if you go this route, look at the other sites that offer games of skill as gambling, most don't do so well.