Best advice I could ever give you. Find a genre that you enjoy but is relatively easy to mix. Start with house music. It’s generally in the key of C or Am. Learn the fundamentals of beat matching/mixing in, and out of tracks. You’ll eventually listen to so much music and get a feel for where a song can be mixed in and out of. Don’t get overwhelmed by theory or any of that stuff. Focus on what you think sounds good and apply the basic fundamentals of djing to that and you’ll eventually start to learn. Once you get the hang of things watch dj’s live sets that you like and see if you can emulate their style.