I highly suggest you take some basic piano/keyboard lessons if you don't have previous musical knowledge. Will help you a ton.
You'll need an interface as mentioned.
Practise is the key to making yourself sound good - you can record stuff, but mixing and effects is a whole different world. Its going to take a looooooong time before you get this on lock - you're questionable is comparable to teaching yourself piano and then trying to write a symphony. It just doesn't work that way, but with time and effort you'll get there.
Also, experiment with different tones and ways to say words - its important to play around.
And don't be afraid to be original. If you can't sound like biggie, you can still sound like YOU. Thats whats important - rapping is self-expression, its not meant to be gangster or thug or to talk shit. Its an artistic medium just as much as poetry or painting.
"You only have 6 posts, so you should probably go with the griffon, seeing that someone with such low posts would never need anything over 12 din. I mean I have just over 100 posts and ski 14 din binders, so u would have to work your way up, smell what I'm steppin' in.......... " - theNUTZ