GarageBand Amplifiers vs Real Amplifiers !

For computer recording, software simulators work well. There are much better and more expensive sims you can buy that do a better job. But for me you will never get the sound and feel of a real tube amp played through a well broken-in guitar speaker.

Using your computer while learning guitar will be fine. But for portability, durability, volume and feel you need a amp. There are plenty of inexpensive small amps with onboard sims and effects that will get you pretty far.

There are so many good entry level modeling amps it's hard to go wrong. I usually suggest to my students the Vox VT's, Roland Cube's or Line 6.

you can definitely start with the amps in garageband, just need an audio interface to plug the guitar in. these range from a simple USB adapter up to high end interfaces.

with a decent amp simulation (like NI Guitar Rig for example) you can get some really nice sounds for recording and make a huge variety of sounds without having to buy a million different amps, mics and effects pedals.

but as has been said, there is no substitute for the volume and feel of a decent amp. plus you will learn what the amp actually does from using an amp much more than from simulations.

either way good luck! much fun awaits.