My personal opinion is to avoid free software and go for something in the 'lite' version of established applications such as Cubase etc.

You'll be appreciative of the ability to use VST plug-ins as well as the option to upgrade at later time if you start to progress.

The trouble with free software is that it's usually very limited and not very reliable. Especially when it comes to syncing up tracks.

I'd also avoid GarageBand etc... because they're aimed at amateur musicians who just want to use generic loops to produce music.
Anybody in the know will be able to recognize that your songs are nothing but
pre-purchased riffs rather than something original.
(think..Band-in-a-Box... nothing but a set of generic and slightly cheezy background music meant for the mass consumer who have no real talent for music.)