I always am thinking about the gaps in my "locker" and what needs to be filled. It usually comes down to what will benefit any upcoming jobs vs what I am willing to spend. I own all condensers which include several high end small diaphragm mics of various patterns models and a couple nice large diaphragm mics which I find less useful in my type of recording. I have a couple dynamics which I never bother to use except for live sound reinforcement. My next purchase would have to be a couple ribbon mics since they are as useful as condensers, have great off axis rejection if needed, and usually sound wonderful on just about anything. I was looking at a couple AEA N8's since they have a similar sound to the R88 which is great for ensemble miking, they are durable for location recording, and they are active, which means I'll have less worries about amplifying them.
That is just me. I would just suggest you figure out what you immediately need. If you don't need anything immediately, don't buy anything, save up, and get something better when you do need it.
I agree a good LDC is a must for any studio use. KSM44, C414, Neumann TLM107 are all wonderful mics at any price and are still budget friendly.