Basically some demo stuff to begin with. Simplest I can get away whilst still achieving some decent quality. Guitar, vox, bass, backup vox(?) probably e-drums just to limit processor demand etc. I really would like to see how well I do with it before going too too deep in hard/software. Some people have the ear others, not so much... I don't want to just stick a mic in the middle of the room you know? I want do some actually mixing see how it goes.
You are being too vague... Do you plan on running the instruments line in directly to the interface, do you plan on micing them. How many tracks do you NEED to record at once? Do you want to do a full live setup, or can you record track by track.
If you are looking to just run the guitar/bass line in and processing them in your DAW, you will need an interface with the option for HI-Z inputs. The BlackJack has these.
If you need to record the whole band as one, you are going to need at least 4 inputs you can use at the same time, with phantom power if you are using condenser mics. The BlackJack has 2 inputs, they can be used at the same time and both have phantom power. The ONYX preamps are also the best pres at the BlackJack's price point($150), IMO.
Hopefully, since you are on such a low budget, and don't even have the computer yet, you will be fine recording track by track. With your budget this is pretty much going to be a must if you want to get going right away and not save up longer.
If you don't mind me asking, if you don't even have a drummer, why are you so concerned about recording your own demo? It's a pretty big investment time and money wise for not even having a full band. For what you're looking to spend, you could have your demo professionally recorded, with a studio drummer, and mastered. Just saying...
I can get