It depends on whether you are flying or driving, will you have a cooler, fridge in the room, toaster oven, microwave, coffee maker, etc.
Since we drive we bring a cooler. A few times we've had a fridge but most often we don't. Sometimes we bring a toaster oven, and the food courts have them if you can't bring one.
We bring lots of snacks and tupperware to make sure foods don't get smushed. If we're on our own (no dining plan), we eat breakfast in the room (granola bars, pop tarts, cereal, toast, coffee, juice, etc.). If you have a coffee maker you can make oatmeal.
For lunch we pack sandwiches, juices, chips, fruit, etc., and eat in the park. For dinner we share CS meals. You can always reverse this, depending on how tired you are - you can eat CS in the park and eat dinner in your room. Again, if you have a coffee maker, you can make any "instant" meals like mac n cheese, noodle bowls, soup bowls, etc.
A CS meal will cost about $10 (entree and drink). Snacks in the park (drink and food) are $2.50 to $5.
Your budget will depend on your personal preferences and what appliances you will have on hand.