I don't want to be offensive at all man...seriously. But you need to eat more to gain weight. The "rules" don't apply for all of us as some of us have to eat a lot A LOT more food than others to make gains. I was 154 when I started training, was 291 last week.
I also understand eating on a budget...it is hard sometimes. We do the best we can.
Good Advice!!!
Hard Gainer = Under Eater
No mater what program you do, if your diet sucks, so will your size and strength gains. Try to eat 3 times your body weight in protein and 2x body weight in carbs and fats. If this doesn't work eat more.