I knew I should have gotten 3. So I think I will get one more for christmas lol.
Maybe get two, if you can. To me, a good 'basic studio portrait set up' is 4 light. One as a main, one as a fill, then two as background lights (for high key) or when doing low key, one as a hair light and one as a kicker/accent light. You can still use one as a background light for low key, to give a spot or gradient to the backdrop, as seen in kudalini's example above.
I have 4 Bees. Two 800s and two 400s. And that's pretty much how I would use them in those situation. I do have half a dozen (or more) other strobes that I could use when need, but I think that three or four are enough most of the time.
Also, you do seem to be learning your lighting pretty well...but most photographers will say that they wish they had learned with just one light. Doing everything they could with that one light, until it became absolutely necessary to add more. All too often, people go out and get 2, 3 or 4 lights and try to start using them all...which really makes things a lot more complicated than it needs to be.