Meal prep

Are you wanting to prep for the entire week? Tomatoes and avocados don't hold up well, in a dish, for more than overnight imo. But mash it and add lemon it will stay a little longer prepared but still separate. Soggy sandwiches make me sad. I usually pack the ingredients as separate as possible to grab and go. I do this with tacos too.
I usually pre cook and cut veg and store them so I can make a quick lunch if I am able to get home to eat.
I batch cook soups and freeze in pint Mason jars. I take them out the night before and put in fridge, they keep everything else cold and are thawed by the time I eat. I do this with bean burritos too.
Can you warm things up?

Fresh fruit and veg don't tend to reheat/keep super well for meal-prepping.

I usually stick to cooked dishes like casseroles, curries, rice dishes, pastas, quiches, pies, stews, soups.

Mason jar salads work great as well and keep fresh for a full week if you layer them properly.

As for pitas... I'd probably just prepare the chicken in advance then assemble them as I need them.

For weekly meal-preps I like to put enough portions in the fridge for 2-3 days, then put the rest in the freezer and replenish the fridge as needed. It keeps everything tasting fresh for longer.

i usually meal prep tacos or one bowl dishes. Tacos I pack all the ingredients separately and then warm them/combine during my lunch time. With the one bowl dishes I usually freeze those in baggies and warm them up in a bowl during lunch.