I agree with Mark 7.
I recommend starting with Cubase SX as it is advanced yet extremely easy to grasp and get control of after watching some tutorials and understanding the basics. You Tube is great for tutorials. Multitracking wise, sequencing midi, editing midi, working with audio, editing audio, adding effects, time stretching samples, all very easy to do in Cubase
You'll need a decent sound card / audio device (I recommend an M-Audio product to get you started as they are affordable) and a decent midi controller, again, M-Audio Axiom is nice, and some headphones (Sony MDR 7506's) if you can't yet afford Monitors (KRK's are nice and very affordable.)
You'll also need a handful of VST/VSTi and Plugins. You'll need to build your drum library. I recommend Native Instruments Battery 3.
Once you learn Cubase SX (A year or two of using it) you can move on to something like Pro Tools 7.4 M-Powered if you do purchase an M-Audio soundcard, and learn the industry standard.
Reason, I recommend getting this also, but only to Rewire it into something like Cubase or Pro Tools. Strictly as a DAW, Reason doesn't meet the standards, it's more or less an excellent rack of instruments, modules and effects.
Research. Plan. Budget. Purchase. Execute.