As much as people try to diminish the usability of Garageband, it's a decent DAW, and some big artists started out using it! If you happen to like that and start to outgrow it, Logic is probably your easiest route. It's a bit more complicated and has more features, but it's like Garageband had a parent, and that parent is Logic. It's a very smooth transition between the two(sorry if you've already been told the same elsewhere) Good luck, and have fun!!
Also, here are some links for free samples - some might seem odd, but you never know where you might actually end up using them:
http://www.embertone.com/instruments/instruments.htmlhttp://www.atomhub.net/Freebies.htmlNot free, but cheap and whimsical:
https://www.audiothing.net/instruments/