Ok i ordered some basic things except for the jumper wires.
Question: I have a computer power supplier that won't be used anymore.
Is it possible that i cut the small cables and use them as jumper wires or is it different from the usual ones?
It depends on the size of the wires in the pc. Maybe they will fit the Uno, maybe not. I had some hook-up wire that would fit some boards, and not others. So I got the various collections of 22 gauge jumper wires, and everything works. For wiring, you really want different colored wires so that you can follow the circuits better.
Note, you will also need to strip the ends of the wires. If you are going to be doing a lot of wire stripping (probably not at first), you might want to invest in better wire strippers than your usual pair of needle nose pliers. But if you are just stripping a few wires, any pliers (or even a knife) will do.
If you live in the USA, Radio Shack sells solderless jumper wires for $6.29 (http://www.radioshack.com/product/index.jsp?productId=2103801&retainProdsInSession=1
). While you can probably get such jumper wire kits cheaper via the internet, you might not want to wait 1-2 weeks.
Oh, and have fun by the way!