Usually I just buy 2 crickets and give them to my t's (as I only have 2 t's)Remember you need to feed your crickets with good quality food. A colony of Blaptica dubia is very good to have.
I don't usually leave them (crickets) to sit around long enough to have a meal of their own.
But that being say, is a diet of just crickets enough for slings?
(since I cannot get anything else other than worms)