Before you start worrying too much about the finer points of your diet, start by getting a baseline for how many calories you're currently taking in and what your rate of growth looks like. Ultimately, growing demands more calories. Because you're unable to do many of the "money" exercises like squat and DL, you should probably be pretty conservative with how much you add to your diet. Experiment, weigh yourself, and keep detailed notes about how many calories you're taking in.
A lot of the diet stuff people will tell you are things you probably already know. Bagels with cream cheese, pretzels, and baked chips aren't exactly "muscle food," ya know? Think of people who have gotten big and strong in the past--they were typically eating whole eggs, steak, cottage cheese, chicken and beef, etc.
Some basic foods that are acceptable depending on your macronutrient goals:
meats--lean beef, chicken breasts
nuts, nut butters
veggies--broccoli, spinach, peas, etc
cheese and dairy
That list isn't comprehensive--there are tons of others. Whole foods, unprocessed stuff, etc.
Personally, I would recommend going for more in the way of fats and protein than carbs. But if that's too much for you at the moment, then just focus first on your overall calories and that you're eating sensible foods.
What does your current training split look like? How much longer until you are able to incorporate leg work into your routine?
And ultimately, I'd advise that you just start reading articles on this website. This site has an amazing amount of useful information about all this stuff.