Any tips on making quesidillas?

To piggyback on this comment - if you normally use store-bought tortillas, try making your own instead. They're easy and cheap to make, and taste way better IMO. (Plus they won't have all the preservatives and other additives).

All you need is flour, a fat (traditionally lard, but I've also used butter, ghee, olive oil, or bacon grease with good success), some salt, water, and a skillet or griddle. Some people also use baking powder, but I think it's fine without (I prefer my tortillas to be chewy rather than fluffy).