If you think african ciclids are a pain, you will be in a world of hurt with chameleons regardless of the species.
My suggestion would be crested gecko's if you want something arboreal. No real UVB lights required (though I use them.) No real temp issues as they like ambiant temps that are in the home. They can eat babyfood (or T-Rex diet) +/- insects. They are pretty friendly and will handfeed without much effert. Don't mind being held and come in a variety of colors. You also can keep multiple animals in an enclosure without problem (no multiple males). Only down side is that humidity has to be kept high. Also they are nocturnal, so they really become super active until like 10pm-4am.
I agree that beardies or uromastyx would also be a good choice for a tank that big if you are looking for a larger lizard. Blue tongued skink may also be on that list, though now you start talking about UVB bulbs and increases in heating requirements. You also start talking about increased efforts in dealing with nutritional demands if they won't eat pelleted diets. Probably more expensive to keep than geckos.
If "not too expensive" is one of your prerequisites, DO NOT get a chameleon. These little buggers are expensive pains in the ass. Most of them are pretty ungrateful. Mine gives me the hairy eyeball every day when I feed him or just walk by his cage.
Don't get me wrong, I find him interesting and hilarious, but I'm not dillusional about our relationship.
Good luck,
Matthew