Exercising tips?

Since people have been asking questions regarding health, I have some as well. I want to know what are some good ways to gain muscle mass, eat healthy without it being expensive or time consuming to make (I'm a broke, full time college student that's like $11k in debt) and if you work out - what is your routine?

Here's some info on me: I'm 5'2, ~100lbs (157cm, ~45kg). Because of my genetics, ass and thiccness has not been bestowed upon me and I have a hard time gaining mass literally anywhere but my belly. I'm not looking to be model status but I really want to work on my arms and legs so I don't look like a pear with chicken limbs.

Please be specific as possible. Like what specific work out uh moves?? position?? lol idk you think would help. I am also a flexitarian (I only eat meat on weekends for personal reasons) so I am really open to vegetarian dishes. Also, you're welcome to share your own stories, I would love to hear about them.