Agreed with above except for the Chameleon skinks. Just have never found them all that useful, or at least being able to do a job that my cheaper skinks (or Terridons) couldn't do and generally better because there are simply more of them.
Essentials to the army are skinks with a few saurus to lock enemy units so your skinks can get the charge. Think of it kinda like the human body, the saurus are the heart and skinks are veins, and the more you have the better (within reason of course). Core aside, the only other necessary unit is a unit of at least 3 terridons. Lizards need to knock out those enemy war machines and terridons are where it's at. cheap, fast and they drop rocks on any unsuspecting unit of fast cav they happen fly over. Just watch out if you field more than 1 unit cus some people will start shouting cheese. Everything else you decide to field is personal preference.