How would I go about gaining muscles?

go running dude, get that cardio in, go to the gym. 50 push ups is only going to work part of you muscles. if you dont do cardio, you wont get anything. eat lots of protein, shakes, bars, maybe creatine if you wanted to.

Oh god 50 push ups a day will do **** all sorry I'm 15 and I do 350 to 500 push ups a day and that's what gets you muscle I'd suggest eating a lot of protein and doing press ups every single time you can at home like do 50 then wait till your arms refresh then do another 50 and so on untill you get weights and you can use 30 pounds to get muscle at your age just use them alot

start using your weights to do some curls and extensions so that you are doing 8-10 reps with the last 3 reps being very tough. try eating 6 small and smart meals a day (7am-10pm). try doing different variations of pushups that are harder i.e. decline, military, dive bombers, etc. eat carbs late at night to build mass.

eat lots, protein shakes, and lift heavy