At Camden Yards you are allowed to bring food and drinks into the ballpark (the drinks must be unopened and in plastic bottles). There are plenty of vendors who sell cheaper hot dogs, drinks, and chips combo outside the stadium that you can just bring in yourselves.

If you plan to eat in the stadium, buy a ticket for the left field club seats with the meal option. It's a lot of food for a reasonable price compared to the regular vendor prices. A real pro tip for when you leave is to not go to the Camden Yards light rail station if you are going southbound. Everyone new seems to go to the Camden Yards station when in fact there is a station just as close at the Convention Center pickup that comes before the Camden Yards station.

Since the Park allows you to bring in outside food, pick up you peanuts and pistachios from one of the outside vendors, or even better pick up a pound bag of peanuts at the supermarket and take them with you.