At 19 your hormones are sky high, you don't need gear. At 6'-4" and 155-160, I would say you need to learn how to eat before anything else. Don't buy weight gainer or protein thinking that will solve your problem of calories, if you do use these only use 1 or 2 a day. Food is what you need and lots of it.

At your height you should be able to hit 225 2-3 years and maybe 250-260 by the time your old enough to juice, which is around the age 25, if you start before that you need to have you Dr check your growth plates, to make sure their closed.

Now some could say he's 6'-4" growth plate doesn't matter. Growth plates close at about the same time as your hormonal system is fully developed. You don't want to shut your hormonal system down when it's still developing, that could cause major problems in the future.

JohnnyB