I dont have a pressure gauge on my pump, so i just follow simple females advice that:
"The harder it is, the better it is".

Seriously though, with an Average sized diameter leading edge id say 6-7psi; with a small diameter LE (Nemi HP etc) up to 9-10psi...
Another alternative is to pump the kite up until it makes a nice "ping" sound instead of a "doof" sound when ya flick the L.E.