A guitar cord with usb on the other end would definitely be a top pick, but you’d still want to eventually buy a recording program to go with it.

But if you have a little bit more cash you can buy a recording interface that usually comes with a recording program.

The Line 6 GuitarPort RiffTracker has different amp models to chose from so you can build your own custom sound, and is priced at $190

Or, the M-Audio Fast Track comes with GarageBand for about $100

I use the M-Audio Fast Track Pro and I love it.

You can get a chord that’s like a regular instrument cable but on one end is a USB so you can connect it to your computer. Here’s one: