If you can learn to make your own energy bars, these are great for backpacking trips! I like to use this formula:
Invest in a portable one pot stove for backpacking and you can make oatmeal, cream of wheat, vegan bannock, red lentils and sundried tomatoes and more on the trail! But even if you can't afford a stove, you can get by. I get these little peanut butter individual packets from grocery stores that is called Justin's (they make peanut butter and almond butter). I am not crazy about them due to the palm oil, so I have also ordered bulk peanut butter individual packets online at Amazon.com called "Wild Friends Unnatural" that is straight up peanut/nut butter without palm oil or other stuff. I add it to a tortilla, roll up the tortilla and eat it as a snack on the trail. Sunflower seeds or pumpkin seeds with shell on are great too! And nothing beats fresh fruits. Most will keep for days on the trail. Dried fruit keeps much longer, but of course it is more expensive.
Whole grains are also good sources of protein. Couscous is cheap and cooks quickly, as do oats. Brown rice has good protein and is very cheap.
Leafy greens and broccoli are protein sources in smaller amounts but have other nutrients like iron, magnesium, calcium.
Beans are your best bet, especially lentils.
Nuts are very high in fat and not as good a source of protein, but they are decent. Choose whole almonds or walnuts (high in omega 3 ALA). They are not cheap though. Seeds tend to be slightly lower in fat and higher protein and are a little cheaper, especially if you buy them with the shell on.