Best Beginner Lizard/gecko/chameleon?

[ScottishFish]

As the title says, what would you recomend as a good starter species be it gecko, chameleon or lizard?

As xmas is approaching I am hoping my parents would get me a small reptile of sorts, I have some experience with reptiles already as we have a hermanns tortoise. So temps, heat lamps, thermostats etc I am already used to deaing with.

I have a large storage area along from my dest that I was going to convert as a vivarium with some DIY. Its measurements are approx 18x20x18 lxdxh, so its almost square but slightly larger going from front to back.

Things I know I can get my hands on here, just from memory in lfs, is; chinese water dragons, leopard geckos, regular green chameleons, iguanas. I know the water dragons and iguana grow too big but that's just to give an idea of the range of things we can get here.

Snakes are totally out of the question

Cheers folks!