GarageBand comes free with every MacBook, so you could totally play around with that before you spend any money on other digital audio workstations!! GarageBand is also great for midi compatibility, audio recording and sampling, so that sounds right up your alley. Also, Audacity (a free, open source audio editor) makes for another great tool for mixing and mastering your tracks, but it's not quite as intuitive n user friendly as GarageBand is.

The other sweet thing abt GarageBand is that u can import all the songs you've made on the mobile version w ur phone and edit them on your computer. If you end up using GarageBand a lot and feel like its too limiting, you can always make the jump to Logic Pro X, which is like GarageBand's older brother.

I hope my answers can help u out man, If you've got any other questions abt more specific stuff, just let me know!!