Basically a RAM disk is a very fast but volatile storage. It makes sense to put there files that are often read and written, and preferably whose loss is not fatal. This is because if for some reason, e.g. a power loss the system restarts, everything on the RAM disk will be gone for good.
So yes, you could put your frequently used applications there as well as the you are working on. The latter probably will be more beneficial, depending on the size and amount of files you are using.