Alright i've been working out for awhile, you already look really lean so you'll be better off putting on mass. Don't start buying all kinds of CRAZY supplements. The only supplements you will want if you decide to buy them are as follows : 100% Whey Protein, Creatine, and possibly Casein. Those are pretty good . Now, what you'll want to do is "heavy" weight low reps (Ex. As heavy as you can but 6-8 reps). You can also try drop sets meaning you start with a decent weight first set, go up, continue three times. It'll put mass on faster and make you stronger. If you have any questions don't hesitate to ask .