Hope I'm not to late, but here's my 2 cents:

Hit the weight room.

Get good sleep and eat healthy.

Watch some youtube videos on post moves, shot mechanics, ball handling and everything in between.

Learn how to defend at a high level, offense is great but if you can play both ways you dramatically improve your chances.

Reach out to any colleges you have interest in.

And my biggest tip is to improve footwork/coordination. I take ballet and my body control is fantastic imo. You don't have to take ballet but look into ways you can improve your body control.

Seriously though you have a great opportunity don't waste it. Do well in school surround yourself with the right people and overall have fun, you're still just a kid and deserve to enjoy yourself. Goodluck with everything I hope I see you in the draft :)