I'd say not to be afraid of applying to higher caliber institutions, your degree is just as valid as any from a high ranking university. If they don't want you, fuck them. For lack of a better reference, feel free to apply to programs typically ranked in the top 50. Of course, you shouldn't be looking merely at ranking/prestige, make sure that wherever you apply suits what you want. Think about how much location matters, do you want to live in a city or someplace more rural, how big of a program do you want to enter, and of course what are your research interests. For example, if you want to do drug discovery then there's no point in applying to an organic chemistry program which focuses more on polymer synthesis.
