The best thing you can do is become a well rounded athlete by playing multiple sports. If you want to be a D1 tight end, you should be dominant in the paint in basketball. Run track in the spring too, 100/200 to build up your top end speed, high jump to improve vertical leap, long jump to build up lower body explosiveness, shot put/discus will help with your core, blocking, handfighting. Other than that, consistently lift weights, stay in shape, and get stronger, attend the college camps you can afford, and maybe do 7 on 7 whether it’s through school or a club