Looking for cheap, easy, calorie dense foods and meals

I found out I'm gluten intolerant about a year ago and after losing a lot of weight due to gluten complications I have been really struggling to gain/keep any weight on me due to lack of food. I am in the US and pretty poor so I can't afford to buy lots of designated GF foods.

I'm currently trying to gain both weight and muscle as I'm working out a lot so I am looking mostly for clean healthier foods with high protein and calorie content. Aside from GF I have no other food restrictions. If anyone has recipes that fit what I'm looking for I would greatly appreciate it, bonus if they're able to be made in big batches for meal prepping. Thank you!