Think in layers: something warm, something fresh and something bright.
Start with a filling you enjoy, such as seasoned beans, roasted mushrooms or vegetables. Keep it manageable enough to fit inside the tortilla without overwhelming it. A taco should be easy to pick up, not a balancing exercise.
Add contrast with shredded cabbage, finely chopped onion or another crisp vegetable. A little salsa brings moisture, while lime adds brightness. Taste the components together before adding more seasoning; a lively topping may already do most of the work.
Warm the tortillas according to their packaging and bring small batches to the table. Let people assemble their own, with stronger chilli on the side. A few well-chosen components make a more coherent meal than a crowded collection of toppings.