I dont know what GOOD advice i can give you cause im nowhere near as experienced as half the guys on this post. However in the 2 months that ive been putting my own studio together/banging head against wall, ive learned a few things that i wish someone woulda to old me before i got started, so i guess ill tell you and you take or leave what you want! First thing i wish someone woulda told me when i started is, MAKE SURE YOURE RUNNING WINDOWS XP (if youre a pc guy). If you use a mac youre probably fine but when youre new you dont think about things like a compatability issue. And no one thinks to tell you. I dont know much about vista, but win7 is a GREAT os but is also a great hassle for a number of reasons that i wont get into to keep this post semi short. IT does not look like engineers will be leaving behind xp anytime soon so stick with that.
The other thing is like one of the other posters said, MIDI is not recording audio. Theyre called midi controllers for a reason, like when you play one of those games on the wii? Youre swinging your arm around with the controller and the samurai on the game does the same thing, but youre not actually fighting in real life. With a midi controller say you play a C chord and then a D chord on your keyboard, the computer will receive data saying you held a C chord for this long and then a D chord for this long, but it wont be played in the voice you selected on your keyboard, (if you use a keyboard that also works as a midi controller), but rather whatever voice you select in the software synthesizer you use. Im sure someone here can explain it better than i can, i understand if its confusing. another very important thing, im sure this is a no brainer to most of the people here, you will be doing yourself a world of good to learn the difference between inputs and outputs, its not that hard to understand but it can get confusing once you get to talking about things like monitors (or at least it was to me). I guess the only other thing i can tell you is do your research. I mean more than just read up, if youre at sam ash or guitar center or whatever is your store of choice, and youre thinking about buying a product and theres info you want thats not on the box, then AsK. WHat you ask will usually be a common sense answer to someone who works there but so what if it makes you feel silly, youll feel even more embarassed driving back the next day to take back a product you didnt even know you couldnt use when you bought it yesterday lol. Or maybe that was just me

.
So:
1. make sure you got XP OS
2. If you want your song to sound as it does on your keyboard go audio, not midi
3. Get an interface that has its own preamps and phantom power.
4. know the difference between input and output (believe me if you dont youll walk out of the store with some 20 dollar cables youre never going to need lol)
5. If you want to know something about a product ASK, no matter how silly your question might be. Just remember if you gotta take something back they wont be so happy to give you back your money.
I know this aint the best advice but i hope it helps!