I've recently slightly changed my method/approach so ask me that again in 8 months from now. As for monthly returns, I aim for 5-10% as a lot of traders do (as Rick said).
For example, last month (Nov) I did 7.4% which I'm happy with. I've averaged about ~7.1% for the past four months. I'm quite a conservative trader now and only make 6-8 trades per month (average), risking only 1-2% per trade. I could achieve a lot more.. if I risked a lot more but I could also lose a lot more.
Monthly returns is a topic that's often hard to explain to new traders. They seem to think their $2,000 account will be $200,000 in less than 12 months and it simply doesn't work like that unless you're gambling and taking huge position sizes relevant to your account. In which case, you'll most likely blow up anyway. When I was learning I once met a guy that bragged about turning $2,500 into nearly $45,000 in six months. I met up with him one month later and he'd given it all back.. and some..