Why do you need a pressure gauge? Pump it until it feels hard enough and/or you get tired of pumping it.
I find the pressure gauge a more useful tool if I get a flat in the beginning or middle portions of a ride. I prefer to get to a "standard" pressure if I have 30, 40, etc. miles to go. If I'm in the latter portion of a ride or just cruising home at the end of a ride, pressure isn't a big deal to me. I will just pump it up enough to get home.