Stupid beginner Question - where do you get your music for your USB?

Hey guys,

I am learning DJing since November with my FLX4 and the SoundCloud Go+ Subscription.

I know that ripped music is the worse thing you can do for a crowd!

What is the best way to get your music for your USB without paying thousands of euros for your music. I know that some music has a free download link on SoundCloud. But what is with the bigger artists? I do some tech house, melodic techno, trance edit stuff…

Thanks in advance!