How to get music as a beginner DJ?

Hey all,

recently i've been looking to advance some of the small parties I organize from 'just a spotify playlist' to something a bit better. I've always done them outdoors and for free, so there hasn't been much issue with people complaining that they had to pay for 'only a playlist' :-D

However with the fall and winter coming up, i'd like to start of the next oudoors season by having a DJ.. and well, why not learn something new and do it yourself. The main problem I ran into when getting everything together to practice etc is that I actually have no idea how to get the songs for offline play. I saw services like TIDAL that offer a special DJ extension to the subscription to allow you use the songs, but they still require internet connection (which could be problematic if there's issues or whatever). For any more experienced or beginner DJs that already solved this question, how did you build up your track list and how do you obtain the songs legally?

(ofc i could probably download them in shit/decent quality from somewhere and not worry about a thing, but i'd rather do stuff by the book)

Thanks! <3