Help overclocking my PNY geforce 210 512mb DDR2

The 210 is a mediocre card, and you probably wouldn't get much out of it. The components along with it, are probably also mediocre and would have little headroom left.

Your best hope would probably be a volt mod, but then you'd probably need to consider changing the cooler and voiding the warranty. (The cash to change the cooler might be better kept for a new, bigger video card)