One jar of chunky salsa plus about 1-2 cups of your preferred melted cheese sauce = most common budget Texas party queso. Some people add seasoned ground beef or Mexican sausage. Others add a dollop of guacamole (mmm) but neither is necessary.
I prefer to make a thick cheese sauce with milk or cream and a zesty or sharp cheese like cheddar or a milder one like Monterrey jack; it's usually considerably thicker than that really "saucy" broccoli-cheese sauce, so consider just using less liquid. Then, I add tomatoes (diced, canned or fresh), green chilies/jalapenos (preferably pickled, or broiled/charred if fresh; Hatch or poblano are excellent choices), onions (cooked or raw, but preferably lightly cooked, purple or sweet onion), lots of garlic, buckets of cilantro (assuming you're not a cilantrophobe -- I think it's essential to a fresh-tasting queso or salsa) and possibly some hot sauce on top of that if it's too mild. If you can buy premade fresh pico de gallo, it's basically that combo, so use it if you like.