Hey! So about music, it all depends on what your preferred genres and your style of creation (linear or random). You'd have the most fun with some sort of USB-MIDI (piano)keyboard, yet there are quick ways to enter notes by keyboard and mouse by "step-editing".
Have you tried FLStudio? (easy to get into, best for loopy, sequenced stuff)
Would also recommend Reaper (linear, maybe a little confusing--very extensive)
If you prefer seeing a staff, Lilypond (IIRC) works along with other softwares.
KVR, is a good site where you can find extra sound generating plug-ins and setup information, helped me tons at first...
As for online trading, don't forget to send my cut
