Cheap bulking foods?

I'm a 17 year old shotput/discus thrower and I just started up my indoor track season and got back to lifting. I want to take it more seriously now than I had before, so I'm starting to worry about my diet. I'm 6'5" and have always had trouble putting on weight. I'm sitting between 185 and 190 lbs now, but I want to get up to 200 or 210 eventually before cutting for a lower BF%. I've been having trouble eating at a calorie surplus and was wondering if there were any cheap foods I could buy to just throw into my diet for easy calories to help me reach a surplus. If they had protein as well I'm sure that wouldn't hurt, I think I'm getting a decent amount since I have a protein powder but being sure that I have enough can't really hurt.

tldr: Cheap foods that a 17 year old can buy to throw into his diet to help him gain weight? Protein is nice too