the way to gain weight, is to eat healthy, but a lot. also dont do any cardio, or go very light on the cardio.

the goal is to increase calorie consumption vs calorie burning. get some muscle milk and take that 3 times a day in addition to 3 healthy meals a day, then keep hitting the weights, one week do 3 sets of 6, next week 3 sets of 8, going heavy on the weights, but not enough to hurt yourself.

as for roids, do a lot of research if you go this route, they must be cycled to be taken safely, otherwise they will shrink your penis for real. also you can get calciu deposits behind your eyebrows and retain water. its by far not the healthiest, but is the fastest. but who wants a 30 inch biceps and a 3 inch pecker?