You should wait on the weight thing.
As for supplement they're going to tell you not to take them because they are a little extensive for someone who's not at that "extreme" point yet. That being said supplements will help you get bigger and stronger. Don't take garbage off brand things and waste your money. I wouldnt suggest you spend your money on supplements though until you reached a plateau then use them to shatter it. Other than that work on form. A lot. That'll cause muscle memory and THOSE SPECIFIC MUSCLES will get a hell of a lot stronger.