I would always prefer to play at tables of a skill level I know I can beat consistently until I have won enough that the worst bad beat possible on the next level up would be an irritation not an 'Oh my God!'.
I did about 5 months doing 10+PTBB/100 at the $50NL tables before I moved up to the $100's. My roll was over $4000 by then but I wanted to be sure.
You can move up faster if you like but moving up too soon is the most common mistake in bankroll management. At the low stakes it isn't the money per se that causes people to drop out (after all what $500 in the scheme of things?) , but psychologically a long steak of losing poker is very hard to cope with.
Poker is a lot more fun when you are winning
So I would go with getting used to the site and its players and nailing the $10's for a while. Once you've earned a couple of hundred then take a shot at the $20's.
As for MTabling - well provided you are playing winning poker it will smoothe out your ups and downs (more hands played = less variation) but I'm not sure it mkaes that much difference to the bankroll requirements.