Any tips on how to stay on a varied and healthy diet while being

Your diet is almost guaranteed to be shit, so the only option you have is to just exercise more.

Also, stop drinking pop. Buy a large, easily cleanable water bottle and carry that around. It'll save you money too.

Find a hobby that's active. It doesn't have to be a sport if you don't like them. Could be hiking or climbing or yoga (meet attractive members of the opposite sex).

As for food. Eat a lot of subway, heavy on veggies, low on sauce. Make pasta with tomato sauce, rice and beans, buy chicken legs (way cheaper than breasts) and cut the meat off and make stir fry chicken.
Get those frozen skillet meals with pasta and meat and veg, they're only like $6 for 2 servings.

>>17531602
Buy rice and beans in bulk. Buy cheaper cuts of chicken. Take a multivitamin.

Wow, I didn't read the rest of your post. The cheapest way to bulk up is to eat more than you're required calories every day. Check one of those calorie requirement calculators that let you put in your current weight and ideal weight.
If you want to gain muscle, exercise, eat a lot of fat and protein and decent carbs. Of you don't care what type of weight you're gaining, just binge on McDonald's value menu stuff. Tip: you can make a shitty value burger healthier free of charge by requesting them to add leaf lettuce, tomato, red onions, and Colby jack cheese.

>>17531602
Check store ads for what near is on sale. Pork and chicken are usually a good price. Learn to cook a whole chicken and or whole pork loin and use the leftovers. Good source of protein. Potatoes and rice are cheap too.

Check your local churches and see if they run a community pantry. I used to volunteer at one and it was full of staple foods like bread, rice, potatoes, fruits, and vegetables.

>>17531602
Lebanese cuisine is known for being incredibly healthy. Also smoothies with fresh fruit like bananas and healthy juices (pineapple and cranberry) are great with peanut butter or protein powder. Other than that cut out all unnecessary sugar (most juices, soda, barbeque, sugars, and milk that isn't almond).

Eat how you'd eat if you were trying to lose weight/fat but eat more of it. Like >>17531742 said, up your calories but not junk. Eat some vegie wraps or make some sandwiches desu. don't fall for the ramen noodles meme.

>>17531602
Buy beans and rice in bulk, cheap frozen mixed veggie packs. Buy your choice of meat on sale. This is cheap and will cover your bases. Learn how to season food and you'll be good.