My advice (as a collector, myself) is to only collect what you really enjoy (and can afford) and don't bother wasting any time, money or effort on anything else just because you think it may increase in value or someone tells you it might be a good investment. I've seen a lot of other collectors of various things, get burned financially trying to predict trends or by getting in late on a passing fad. If anything you own ever does appreciate in value, consider it the frosting on the collecting cake. :)