Should I play with a 600$ initial bankroll?

I've got bored of trying to win a free roll been two weeks it's so hard to get any money out of these free rolls!

I'm thinking of just depositing 600$ today and starting as I can't be bothered waiting for any more free rolls. They've kind of been drilling the enthusiasm I had for poker out of me - keep finishing 90th in a field of 12,000 is kind of dissapointing!

So... What limits can I play please, sensibly. Thanks.