The ability to personalize fast food burgers to your liking is their biggest feature. I'll list a couple options for each component that will help you save money, reduce time, or maximize flavor.
Any choice you choose, bread is good. Although I like brioche, a traditional burger bun can also be delicious. Getting a tasty toast on the bun is the most crucial item to think about. For a richer bread, you should ideally toast it in butter or dry in a cast iron skillet.
You can use a device like this Kitchen Aid Meat Grinder Attachment to ground your own meat if you really want to go all out and make an incredible burger. You should go for meat that has a good amount of fat.
American cheese is typically used as the topping on fast food burgers to give them a classic flavor. But if you're more of a real cheese person, an old cheddar will offer a little more tang. Slices of mozzarella cheese are also a great complement to burgers.
Whatever you think of McDonald's, the Big Mac sauce is arguably the best burger topping. These days, a lot of supermarket stores sell it, but I always suggest preparing your own. This is a recipe for Big Mac sauce from McDonald's that beats out any restaurant.
The standard toppings for a traditional fast-food burger are onion, lettuce, tomato, and pickles. Any kind of these will go, but my favorites are iceberg lettuce, dill pickles, raw white onions (soaked to take the bite out), and beefsteak tomatoes.
One of my favorite tips from In N Out is to brush one side of the uncooked burger with mustard before grilling it. It gives the burgers a lovely caramelization. Another piece of advice is to season the patties just; don't season the meat itself.