Reply to Digital DJ Startup Gear

So I'm going to be getting some money soon ($300) to be exact and I am planning on using it to startup Digital DJing around Mid-Michigan.

My plan at this point is to buy up a Traktor Kontrol X1 and upgrade from the LE that comes with that to Pro. All in all this will cost 360 (I'll save up the other 60). My dad and I have a little deal where if I work for the money, and I spend it on stuff that is expensive, {like gear, he'll kick some of the cost if he can. So I'll hopefully have a little extra cash on top of this 360.

My question is, if I do end up getting a little extra coin, what should I drop it on? Should I buy a soundcard and if so which one (I was believeing about Audio 2 or Audio 4 but I'm a little confused as to what the benefits of the Audio 4 are anyways) or should I buy a small mixer? I have no idea where to look for INEXPENSIVE mixers that are still quality. All I really want from the mixer would be to control volume fades and a crossfader though, so I could probably build my own little midi-box for that if it would be cheaper.

In my dreams I'd have an X1 with a mixer like the XONE 22 or 42 with a midifighter or two and then some turntables but that is alas just a dream.

Thanks