i would suggest a under tank heater for a leopard gecko 
and the temps should be 88-90 degrees .. and a cool side of like 75 ? i belive .
use a digital therm for it comes in handy for the temps or a temp gun
if you cant control the heat theres reostats and thermastats you can buy either at a pet shop or the internet.
have you tryed meailie worms those seem to work best for a staple for leo's .
also with crickets ( i would take all the stuff out of the cage so they can see them )
i would suggest super worms to big ,
you should have 2 normal hides in the cage , one hot one cool side
and of corse a humid hide .
the hides are simple really go tot he dollar store and pick up a small plastic container and cut a little whole out , for the hides.. i also use a plastic containor for my humid hide ( i put paper towles in it and use a mist bottle to sptay it
i make sure its alaways misted and moist for my leos
you also should have a small dish for water ( clean water every day ) and i use a dish for meailie worms ( as if you choice to use them or not ?
also a small jug lid is perfect for there little dish of pure calcuim they need in the tank .
as there food should be coated too with calcuim so they dont suffer from mbd .
( I suggest a book for leos , to help you too ) very helpful for begginers trust me 
i hope this is a bit of info ?
show us pictures
.
have other question's ask me ill help the best i can
Christina