Legit, your first thing to try is a taco. One soft, one crunchy. That's actually the best and simplest food they have. You'll get an idea if you actually like the way they tend to spice things, and that matters because it's where most of the flavor comes in. Then try the dorito version. It's disgusting, but in a good way.
There's really nothing to outright avoid unless you have a sensitive gut. They don't have much that's super spicy, and they mark it clearly. But the grease factor runs very high on all their beef options, so if that's not something your gut likes, you will be spending some of your next day jogging back and forth to the toilet. Since that grease tends to pick up any spice, the hotter options amplify it.
Being real, Taco Bell doesn't deserve the hate it gets any more than any other fast food. It ain't real Mexican, it ain't real southwestern or texmex either. It just takes "inspiration" from that kind of thing.
Now, back in my younger days, running d&d games with other teenagers and early 20s monkeys, taco bell was the only option late at night for those long sessions. So I ate way more of it than I should have lol.
My personal favorite was the 7 layer burrito. That shit was bomb. But you can mimic it. Order a cheesy bean & rice burrito change it to "fresco", add three cheese blend, lettuce, guac, plus tomatoes and sour cream. You will be farting! But it is worth it.
Now, the "Mexican pizza" is another classic that they're famous for. My best friend was super into them, it was all he ever got back in the nineties. It's not bad. Not great, but not bad either. Kinda just a taco with extra steps, but the way you end up eating it has the ingredients hit your tongue in different ways.
There's the black bean crunch wrap supreme too. It's a giant, fart causing calorie bomb, but the black beans really are nice.
I find chalupas and gorditas to be a gimmick that isn't worth the extra cost over tacos.
One of the surprisingly addictive things they have is the grilled cheese burrito. It's kinda nuts. 700+ calories. Beef, rice, cheese sauce, sour cream, cheese mix, chipotle sauce, and "fiesta strips". Now, I have no fucking clue what is in the fiesta strips. Maybe it's chitlins made from the guts of immigrants, maybe it's a magic spell, but fuck me running, they make that fucking burrito rock. It is a gut bomb from hell, but it's worth it.
You kinda gotta try the cinnamon twists too, even though they're kinda shitty. It's like the downs syndrome version of a churro.
Thing with Taco Bell though, you gotta get the sauce packets. Mild is mostly pointless tbh. It adds a little zing, but you have to use two packs per taco to really notice it's there. The hot is probably not going to do your gut any favors, but calling it hot is a bit of a stretch when it comes to spiciness in the mouth. The fire though? You'll know it's there even if you just add a little. It'll make your lips tingle a little. I don't recommend the Diablo unless you like heat over flavor. If you really like heat, buy a better sauce that tastes good as well. It'll light you up decently, but that's really all it brings imo. The other "levels" have decent flavor under their heat.
Their quesadillas are all "okay". They're basic, mild flavored, but can fill you up decently. If I go that route, I like little extra sour cream on the side and a generous drizzle of sauce.
Again, don't expect this to be some kind of 5star dining. It's cheap, it's fast, and it's designed to hit you with enough salt and fats wrapped in some carbs that you'll feel plenty full. If you want something with nuanced flavors and depth, taco bell ain't it. But there's really no other chain food like it.
