I use 3kg weights,do push ups,and if needed for some muscle gain i can do pull ups.
Bigger weights i can not get,cause i dont have,and i can buy a pull up bar if needed.
I can barely (don't think i can even) do 1 clear pull up,so i must gain some muscle.
Will these 3 options help?
Thread: Muscle gain for a 13 year old.