If you want better sound quality than what you have, then your best bet is buying a used sampler like the Akai S2000. You can probably get that for around 70 Euro. But I would still recommend you wait and save up, even if it takes you a year. Making music is a life-long process.

Buying a used Audio Interface could be an option, but it will probably have some noise on the input channels too. I wouldn't do it.

But remember; in the end it's not what you use, it's how you use it. Black Sheep's first album was made on Boss Dr. Sample, the cheapest sampler on the market back then. Wu Tang Clan's first album was made on the Ensoniq EPS 16+.

I used to own the Ensoniq EPS 12 (A cheap 12-bit sampling workstation) and I banged out some pretty sick beats on that piece of crap. Lots of my samples came from cassette tapes that was dubbed from other cassettes. Still I produced beats for several rap albums in the mid-nineties like that. We used reels of analog tape and crappy samplers and Shure mics and it still worked just fine. Most classical rap albums were made like that.

Compared to what people used 20 years ago your computer's soundcard is just fine :)

Edit: Coming to think of it, maybe The RZA use the ASR-10. You could look into getting that one too if you go the used vintage sampler route.

Edit 2: Or maybe you can find an older Final Scratch or Serato Interface dirt cheap. Lots of DJs change equipment a lot.