Well you would start with, learning your drum machine, being that will be your source of creation: sampling,drum patterns etc.., then setup everything learn how to seperate tracks: kick-1, hihat 2, snare 3, vox1-4 etc
then from their you are on your way.
You may need a keyboard if you want melodies,
with a drum machine all you can do is sample someone else's but if you want to learn to create, purchase a keyboard to play melodies, kind of like that sound in that "forgot about Dre" track, that EMINEM ryhmes over
Nowadays everybody wanna talk like they got something to say..... da da da (that part)