I have a Greek tortoise and 4 Leopard geckos (and 2 snakes), I got the Leos first and truly think they are a great 'starter' reptile. The care is basic, they are hardy and forgiving of minor mistakes and are just plain funny little things to have around. All of mine have very different personalities and all are friendly, social and goofy.
Turtle is great too but takes up a lot of space and requires special lighting. He does mess his table up, coconut coir is always in the water and food bowl and greens get tracked all over...I tidy it up multiple times a day. It's well worth the hassle but the Leos are much easier!
I vote Leos.