I definitely agree that upgrading your heals and wards first is the way to go. However, if you find that you are the only debuffer in your guild, you should upgrade your debuffs next. Not all have a significant upgrade, but they tend to stick longer and make a helluva lot more difference than the minor changes in the group buffs. I believe that Mystics are debuffers, not buffers and therefore you should focus on what you can do to the mob before you worry about what you can do to the group. Of course once your debuffs are upgraded, I do highly recommend your buffs. As far as which ones have best upgrades, well I've done all of them because I feel that most of them will be fixed eventually and when that happens the cost of rubies will go through the roof =)