As has been said, there are a lot of factors to take into account before a recommendation can be made, however, judging by the typical conditions that are largely common to most hobbyists´ circumstances, i think it´s fair to say that quite possibly, the best starter species is Pleurodeles waltl. Other species are equally excelent, yet may not be suitable for every case, but P.waltl perhaps has the broadest spectrum of tolerance in captivity.
Make sure to do as much research as you possibly can before acquiring any animals. Have everything ready, a cycled tank, food cultures, etc. There is a lot to learn before taking the plunge.
Anyway, welcome to the forums and good luck! You´ll find that caudates are extremely addictive.