From the photo it's a bit hard to tell: Looks like a nigrolineatus.

Look at this German site for ID:

http://www.grisus-welt.de/Gerrhosauridae/Gerrhosaurus/Gerrhosaurus_flavigularis/gerrhosaurus_flavigularis.html

Has pics of all common plateds in one place, just click the links on the left.

As for how often/how many: For an adult as many as 20 big crickets or 6 - 8 big zophobas - but watch it, they tend to get fat fast. A day or two of fasting/fruit only are often in order. Don't feed them to the max every day, as they WILL eat way too much.

Try pieces of banana & grapes - these are the favorites of my G.vallidus. And they also *love* thyme flowers for some reason... And strips of cut up chicken/beef heart.

HTH,
Kai