There are two things you have to know before deciding what lofts to get for your wedges. Firstly, how many wedges do you want? This will almost always be three or four. Secondly, what degree is your iron set pitching wedge (assuming you are not replacing this as well). As technology has advanced many leading manufacturers have favoured stronger lofted clubs and a pitching wedge loft can now range anywhere from 43 to 48 degrees.
Once you know these two factors, ideally wedges should be gapped by 4 or 5 degrees in loft, but 6 degrees is workable. However, if you have a very strong 43 degree pitching wedge you may have a larger 7 degree gap to a strong 50 degree gap-wedge.
General examples for 4 wedges: 46/50/54/58 or 48/52/56/60 degrees
A general example for 3 wedges: 46/52/58 or 48/54/58 degrees
As long as your wedges are generally no more than 6 degrees apart, the rest is personal preference. I would recommend avoiding any wedges above 60 degrees, as it is unlikely mid handicappers will find any benefit from these clubs. Also, try to find a wedge that suits you and buy a set so that performance is consistent across them all.