Alright guys, i have on question, but i would like only people with experince in taking supplements to answer.

I am 17 years old, and i play basketball at professional level. I have 2, somethimes 3 trainings a day, but now since the school started i only menage to go to 9-10 tranings a week. Now i want to start with gym. My first time in gym was this year in august. i was on my school break and i was going to the gym for a month and stopped. Now, i was thinking how to fit in my basketball trainings with gym trainings, and i need help here. How many times a week should i go to the gym. is 5 times a week to much? Should i take any supplements, since i heard a lot of my teammates do, but they don't want to talk about it. What supplements should i take. will they have any consequences on my health.
Thanks in advance.