What is the best way to gain Weight? Specifically muscle mass and definition?

I'm 20 yrs old male that is 5"6 and 117 lbs, yeah I know, pretty freaking skinny and small. I tried going to the gym but the nearest one is a little over in hour away and the gas prices was killing me so I stopped going. I still live with my parents and there on this NO carb diet, and eat vary little, so there is vary little food in the house. I have a job as a waiter but with them making me pay rent, and my cell bill , and other crap it's hard to fork over money to pay for my own food. Last year I bought some stuff I could use at the house, like the perfect push ups, iron gym, and I bought a bench press with a curling bar also. I was working out, for 6 months 6 days a week on everything, and I was only drinking water and 2% milk. I was trying to eat good, like peanut butter sandwiches and meat but again it got to expensive since I pay for everything. After 6 months I only gained, 3 lbs. So that was a BIG morale killer and I basically gave up. So now I'm on here, yahoo asking since You know my situation what is the best way to gain weight? I haven't tried protein shakes or weight gain pills, or anything like that, do they work? If so can I mix them together? Like take those pills and drink those weight gainer drinks? Which ones on the marker actually work? Or if there a waste of money, what should I do?