His appetite will vary. If you are trying to ration crickets because they only come in certain quantities, I would say 4-6 'head-sized' bugs is a good amount per day.
If you can, allow him to eat as much as he wants, until about 8 months of age. I have a few 6 months olds and some will eat 10-12 or more in a day, and then go 5 days of eating just 3 or 6, then 10 again. It really does vary, and it should based on their appetite. So don't be alarmed if he is not eating sometimes.
Then you can feed him with more of a feeding program like 3 big crix one day, 2 dubias next day, 4 silkworms next day, etc... but yeah for now let him eat however much he can/wants.