Garage Band is a great starter app. There is no need to jump i and buy Pro tools or honking audio interfaces, until you have gotten to the point of actually needing them. If you are just recording audio, and not doing any fancy editing, it will serve your needs. GB also has a decent loop library, drum kits, etc., that can be expanded, and VST plug ins can be added to GB, also. I have both GB and Cubase, and my VST library serves both of them. Since you have been studying GB on youtube, you are on the right track. And check the Apple GB users group, too. GB also is a great teaching device - there are all sorts of how to play lessons for it. GB will do a drag and drop of audio files. iRig works great in GB. it will work in real time.
GB saves all data and audio tracks into a single folder. You can open that and copy / move audio tracks out of that, if you need. One thing that GB does is that it will see into your iTunes library, and import MP4 as well as aif wav and MP3 files. GB will also automatically see you audio interface and set it up for GB. No need for drivers. If you want to use a midi keyboard, you will need a midi interface if the keyboard does not have a USB out on it. If it does, then the Mac will see the midi keyboard through the USB port..
As far as interfaces, I prefer firewire, but that has been more or less discontinued. A simple USB interface will work in the beginning stages - I'd suggest getting a used one, that you can resell later when it's time to upgrade. I suggest getting an external hard drive for backup of your work - this is good advice for any computer.
If you are learning, get iReal Pro. It's a cheap app that works as a play along (no melodies) that has hundreds of songs, including a lot of the Real Book. It displays a Real Book type lead sheet with a marker, and plays the chords, bass and drums. It will change keys and tempos, even styles, very easily, and will display guitar and piano voices for each chord, if you buy the plug in.
GB and iReal Book are available for iPhone, too. Scary...
This :
"I hear macs aren't as vulnerable to viruses and that they're good for making videos and music so decided to give it a go and find out for myself."
This is true. But to be sure, use adblock and noscript with either Safari or Firefox. they are both free apps. Noscript is the virus stopper, and adblock stops those ads that appear. I have been a Mac user for decades and have never gotten a virus. iMovie will share iTunes and GB files, and movies can be dropped into GB
"I'm making a list of these programs to check out.
How would someone share programs with each other if the computer has no cd drive?"
If you mean "Share programs" as in copy, don't do that. that is piracy. If you mean share audio files, email, drop box, flash drives, etc. GB has a "Share" drop down to do that. It will format and normalize to the file type of your choice. And why bother when GB is free?
As well as the programs azure blue suggested, there's a free anti-virus program called AVG that works well, as well as avira and avast both also free.
