I got my panther at 2 & 1/2 months (tho he looked about as big as most 3 month olds I've seen). I really enjoyed watching him change the first few months (still do but the changes are slower and less drastic)
I'd say if he's eating crickets slightly larger than pin head you'd be good to go, they do suggest with live bearers (such as jacksons) to get them slightly older, as they can die for no apparent reason as neonates.