I think a lot of ppl misuse weight gainers. I have seen a bunch of people take them assuming they will get a lot bigger just from that and than forget to eat a lot of food as well. Weight gainers are good if you supplement it with a good diet like Eric said above, just make sure you eat a lot as well as taking it.

I personally will just stick to fast food 1-2 times a day and eating foods high in protein/calories constantly. I am only 20 and I assume have a extremely fast metabolism.
Dollar menus are your best friend.(if you dont mind some fat while bulking/gaining weight and depends on metabolism)
I will be cleaning up my diet at some point