Foro Bicicleta todo terreno

My kid has recently started bmx and is loving it. The issue is I have absolutely no idea what we are doing, this isn't a sport I've ever been around. I'm trying to learn so I can be the best supporter for him. I was hoping I could get some suggestions on the best brand of pants to get. I was also hoping someone could dumb down the sizing for certain brands, they don't seem to be sized the same way normal clothing would be https://tutuapp.uno/ .