Assuming you live in the U.S., getting a gig at the young age of 12-13 years old won’t be easy. I started at 11 and had the same questions and frustrations as you. I began to DJ every party I could even if it was for free, because practicing reading a crowd and learning to play live is important. I did my friends’ birthday parties, a few school dances, and threw a ‘Spring Break Party’ in my friends backyard (which was a success). Eventually I found a mentor, or older DJ who really taught me the craft, and let me go with him to gigs. Through him I learned to practice efficiently, and actually become a better DJ. My recommendation to you is look for a mobile DJ company and see if they would take you with them to help them out at gigs. Mobile guys tend to have connections to DJ’s in the clubs, and are also good mentor’s (depending on if they want to help). Also make sure you’re PRACTICING a lot because as much as you think you may know, there’s a lot of room for improvement.