So I'm graduating in a few days and am treating myself to some camping. I'm packing everything on my back, so it's fairly minimalistic. I am planning on making tunafish sandwiches on tortillas but need something to mix it with (plain tuna is gross), and I'm not a big fan of Mayo. I'm using the foil packed tuna, not canned, in order to save weight. I'm considering peanut butter, but I'm keeping that on the backburner if I can't find a different mixture. Any ideas?

Also: If you guys have any other ideas for packable foods that are high in calories/protein, low in volume/weight, then I'm all ears.
I'm also taking nuts, granola, peanut butter, beef jerky, dehydrated blueberries, and instant mashed potatoes.

I dont eat alot of prepared foods.  I just bring what I eat regularly.

Usually peanutbutter. Nuts. Hard veggies and jerky. Maybe some oats and dried fruits.

Instant mashed taters sometimes but not usually.  For fish I prefer salmon sardines herring or mackerel.

I do some foraging but don't  if your not comfortable

Spam (you can buy spam slices too) is an option to mix things up.  Pepperoni /summer sausage and shelf stable cheese too.

Knorr pasta / rice sides are great.  You can add powdered milk and olive oil to increase calories.

Basically anything with nuts will have a high calories/oz ratio.  This is something I stumbled upon which has a ~1200cal/4.75oz bag:

Take a few limes, squeeze a lime on the tuna.  Take some of the small packages of crackers with cheese or peanut butter, eat the tuna on the crackers.

Congratulations on graduating...

But did you just suggest tuna and PB on tortillas?  Definitely try that before you hit the trail.... doesn't sound appetizing.  I'd get some packets of sauce (raid some fast food places), I like relish, mustard (yellow and spicy), ketchup, taco sauce, hot sauce, you might get lucky with some onion packets.  And if you're have one, the CFA special sauce is pretty good on many things.  Dry chili pepper flakes, dehydrated onion, tomato.   Depending on the temps, you can pack in individual packs of cheese to slice up and put into the tuna as well.  If the tuna packed in oil, then even better for calories.  The dry protein shake mixes or meal drinks (are usually high calorie, plus vitamins/minerals).

Thru hikers often carry a bottle of oil to add to their food - calorie dense.  I like to carry nuts (walnuts and almonds) have higher nutritional value than peanuts, but are more expensive.  dark chocolate.  I also like real bacon in pouch.  SPAM has been mentioned, which I love as well.  You can get hard aged cheese that will keep well... like parm and shave into your potatoes.  Really good with your potatoes.

You don't say where you're going and you might shift things... how your water situation will be.  Carrying lots of dry, dehydrated, etc... requires lots of water.  Test your mashed potato with cold hydration vs hot water (some are fine, others taste like paste... they have starchs that don't bind without the hot water to activate).

I took a family poll no one in my house thinks PB and tuna is a good idea.

"Butthole sandwich" toasted bagel, peanut butter, honey and bacon.  Vacuum seal and freeze will last a couple days in the field.

You do know they sell tuna foil packs in flavors? I prefer the Spicy and Sweet and Lemon Pepper flavors for tuna based trail meals.

I lot of my trail (cooked) meals were based on ramen and Knorr noodle or rice packs.  A typical might be a homemade combo of a half brick of ramen, with a spoon full of flavored instant potatos. This all in one ziplock. Just add appropriate water to hydrate in a cozied ziplock. Same with other dry soup mixes. One might be Minestrone soup mix in a lunch portion with a squirt of olive oil. Just rehydrate and drink. You can get creative with just  $10 worth of larger packs intended for kitchen use. Just divide up, mix and match and calculate water per portion.

A first evening meal might be frozen meat and a spud. Preseasoned and frozen. Keep it in a cooler in the car on the drive to the trail head.  It will thaw on the first leg out from the parking area tp your first night camp. That could be strips of steak on a kabob spit and a foil wrapped spud. Frozen link sausage  has so many preservatives that it was good to roast on on open fire the next morning and downed with an egg boiled in a small tin can or pot.  They make small, light hard cases for eggs that could give you a hard boiled egg every morning for a few days. Frozen meats can be carried in little homemade Reflectix bag to slow the thaw. Chicken meat rots faster than any other meat, so I always avoided it using the freezing method. Canned or foil packs are good to go.

I used to use a lot of Spam foil packs, but about five years ago I ate some strips of spam on skewer on a hike and it made me sick for some reason. It was not bad. I think I'd eaten so much Spam in 40 years that my body developed a revulsion for it. I preferred those stripped and roasted on kabob skewers like the steak strips.

I always liked to carry those mini, one serving packs of tea, hot chocolate,  fruit punch and instant coffee.  Dry gatorade too. Those are real nice for a break when you've been drinking plain water all day. I always preferred the stuff with real sugar. You need it and the electrolytes, IMO.

Of course carry regular "trail" type snacks like power bars, nuts, trail mix and jerky. Those can be real pickmeups on breaks after breakfast has left you.

You can buy the Mountain House/Packet Gormet stuff, but it gets costly and I preferred rolling my own. I'd brew up some homemade meal concoctions to try way before they got used in the woods. Even cook it on the kitchen stove top using my alcohol or butane stoves.

with tuna? olive oil and spices of your choosing. Old bay would be my choice maybe some onion and garlic.