Hm!
Like I say to everyone [or, most people] who ask how to start out, it depends on what you want to do musically! Also, what you're most comfortable doing.
Since you already have reason, you already have a nice set of samples and synths. Work with that and see how you do.
I would recommend getting a MIDI keyboard though, because I hate clicking in notes with mice. Some people are totally comfortable doing this, but I'll eventually get them over to my side. Oh yes, they will become mine...