If you just charge some reasonable amount, and don't sell many commissions, then you can just think of it as having less work you have to do. I go to an arts high school, and when I was putting photography in the art show the art teachers were always talking about how young artists are always undervaluing their work and making it seem worthless to the people looking at it. It's like, if you bought a painting for 5$ it wouldn't seem like you had bought anything where as if you bought one for 50$ it would. Also, if you make your commissions super cheap you'll just get all the freaky fetishy requests from people who don't have any sort of care who draws what they're after.

What I'd do is look at what other artists are charging and set your price based off that. Eevachu does alot of commissions . . . maybe copy his price scheme.

Also though, I'd start doing more free and dummy commissions so you can show people what they're buying.

Honestly, I don't think you should start commisions yet. I think you're good enough, I just don't think you've got enough watchers to sell many. I think you'd be put off by not getting anyone asking for a commision. Plus out of the people who would pay for stuff from you, myself included, very few are actually able. Everyone's penny-scrounging at the minute. I've seen a hell of a lot of artists recently start up commisions, or ask if they should, and have every reply being "I would, but..."
I'd say give it a couple months. You'll build up your fan-base and hell, if you swoop in at the right time you might even benefit from the ol' Christmas spirit ;)