Hi Olihax.
You need to think hard about why you're recording and what you hope to achieve.
If you just want to mess around in your mate's back room, then by all means accumulate bits of equipment as and when you can afford them (the interface and mics first, obviously) and improve your skills as you go.
If you want a usable demo that you can send copies of to venues in order to get gigs then save your money and go into a professional studio for a weekend.
For £500 you can get next to nothing in the way of genuinely useful, quality kit, and even when you do have the equipment you're going to need an awful lot of practice and patience before you have the skills to get good sounding results.
For £500 you can get a couple of days in a pretty good studio with someone who records bands for a living and get maybe a couple of fairly well polished songs as a result.
Don't let me put you off though.
People who want to get into recording need to start somewhere, and if they didn't there wouldn't be the studios for those more lazy amongst us to use.
Aaaaaaaand, probably a better place to ask this question would be in a music recording forum.
Go somewhere like Sound on Sound and I promise you'll get ten times as much information and it will all be 10 times more accurate and useful (no offense to the so far wonderful answers in here, but I'd send people asking Mac questions on the Sound on Sound forum here for the same reason).