theres no secret supplement to building muscle, you need to train hard, eat loads and get plenty of rest.
if your not gaining then 3000 calories a day is obviously not enough, try upping it to 3500 calories or 4,000 calories if that doesn't work.
you should be eating between 6 and 8 meals a day, 3 of which can be protein shakes, meal replacement shakes or weight gaining shakes, the other meals should be high quality, high protein low fat solid meals, chicken, turkey lean red meat, fish, rice, pasta etc. you need to be consuming 1 and 1/2 gms of protein per pound of bodyweight a day.
(i have a protein shake when i get up, one straight after my workout and one before bed)
and its no good just going to the gym, you have to train intensely and get the most out of your workouts, yur workouts need to be well structured to build your whole body without over-training.