I'd stay away from bitcoin miners as these take an initial cost to set up specialist equipment (if you actually want to make any worthy profit, as usually the electricity will cost more than the money you're making)
My suggestion is altcoin mining using your computer so long as it is a decent one (don't go and buy a better one solely for this), signatures are too slow, trading might be a good idea once you gain more from the altcoin mining, or you can go freelance and hire yourself out, which if you have skills, would be my best bet