You should check out digital 8 track machines. The all in 1 set ups from Tascam, Boss, Fostex or Korg all work great, with lots of features like built in effects or some drum set ups, for a few hundred bucks.
Advantages - direct record of guitar, bass, vocals or other - like keys, with built in effects and reverb. On an 8 track you can lay down 8 individual tracks and mixdown to a stereo master mix, or bounce tracks and get more than 8 if needed.
Internal hard drive and easy to convert to mp3 on your Mac or of with a USB connection.
You could also use a computer as your hard drive with a software package for mixing and effects, but you will need an interface to convert your guitar or vocal analog input into digital signal. There are lots of inexpensive 2 channel intefaces, but you probably want to research to find what works well and supports what you need. In both cases you can usually only record 2 channels at a time, unless you get an inteface or digital multitrack that supports more than 2 at a time.
If just you, that is enough to record stereo drum tracks, then lay rythym and vocal tracks, and come back and lay individual bass, keys and lead - with instant playback and editing since its all digital.
I use a Tascam DP-01FX that I got for like $450 5 years ago. I think new ones may be half that now. All the stuff on my MySpace was recorded w the Tascam, either w live synth drums or drum machine.
You should totally get one - it will help you majorly wIth practice / laying down rythym tracks to play lead over and also to play scales over.