You can do what I call a 'dirty bulk', in which you keep your protein high, 1.5-2.0g/lb of bodyweight, and house everything in sight, throwing caution to the wind. This way you pack on an enormous amount of mass, and a generous amount of fat as well, but the weight goes up. A 'clean' bulk is taking caution to the types of foods you eat. still high protein, and then from there, its eating loads of clean foods, like sweet potatoes, brown rice, whole wheat pasta, with the occasional cheat meal thrown in for good measure :)

Its your choice, depending upon your body and how it reacts to certain types of food.