For now, I'm using my Yamaha MTX 4 track ( 6 input channels) as a mixer, with the output going to the line-in of the soundcard on my PC.
So, I recommend a small mixer connected to line-in as a cheap start-up, rather than buying pre-amps and other more expensive devices.
The key is what you soundcard has for inputs ( one stereo = most sound cards versus 4, 8 , 12, 16 inputs of better quality ones)
AND what your software can handle.
Some of the FREE software can only record one track at a time. Is that what you want ?
If you want to record , ex: guitar and vocals to separate tracks, you have to investigate what software / soundcard etc will work for you.
Then, you might want to record a few people, or need 8 or 12 inputs for a live band
I read a recent Canadian Musician article that Firewire is the best way to go, because you usually only have one FW device operating.
USB - once you have multiple devices, including printers, you can get bottlenecks.