We eat a lot of ground beef because it's the cheapest good quality grass-fed meat we can find, but you might also want to look into halal markets if you have any near you. My regular grocery store puts grass-fed ground beef on sale in bulk packs for $3.99/lb but can't begin to match the prices on other cuts with the halal market near us.
One of my favorite things to do with ground beef is to make a simple burger, seasoned with salt, pepper, onion powder, garlic powder and maybe an herb or two, browned in a skillet or on a stove top grill pan and then topped with a generous amount of black garlic butter. The black garlic is not an inexpensive initial investment, but a little goes a very long way, it keeps a very long time, and a small clove mixed into some softened butter is enough to nicely flavor a couple of burgers. Add a side of sauteed greens and mushrooms and a small salad and you have a very wonderful meal.
It's also easy to "stretch" ground beef by making "bowls." Cauli rice as the base, top with matchstick daikon or regular radishes, quick pickled cucumber, wilted greens tossed with sesame oil and 1/8 lb ground beef cooked with a bit of chili garlic sauce. Top with a sunnyside up egg, sprinkle with scaillions and sesame seeds. Yummy and very filling!
Seasons brand sardines are cheap, cheap, cheap at Costco (I know you don't have a membership but just saying!). Boneless, skinless, packed in olive oil and they regularly go on sale for six cans for $6.99. Super nutritious, highly flexible, and hard to beat at $1.16/can. One of my favorite things to make with them is not keto, but do a search for sardine pate (very keto and very tasty with celery sticks). This
Thai Sardine Tomato Soup is delicious, with a little passata and crushed red pepper in place of the sardines in tomato sauce, although I don't know how you feel about tomatoes on your diet.