The main thing is to get something above dime store quality. From there, I like to think about suitability and features. For example, I mainly use so-called high-volume pumps because most of my bikes run large tires and low pressures. I'd rather have a pump with a gauge that reads 0-60 than one that reads 0-220. If the pump you have is suitable and there are no pain points in using it, then you're golden.