With your pin lock kegs, you can purge by pushing on the gas in poppet (use something blunt). Hook it up to CO2 and set about 10 lbs. Push in that poppet 4 or 5 times, waiting maybe a second in between. After thats done, you have very little if any O2 in the headspace. No need to do this again.
If you have some keg lube (one tube lasts a lifetime), use it to coat all of your o-ring seals. This will greatly reduce the chance for leaks. You may still want to pressurize up to 25 psi to assure your lid is sealed. Turn it back down after that. If you have a spray bottle and star san, you can spray around all fittings and valves to make sure you have no leaks. All it takes is one leak and you can blow through a whole 5lbr of CO2 in a couple of days.
Then you just need to figure out how to carbonate. Three options: Set and forget (easiest, invovles chilling beer and setting PSI between 9 and 13 PSI, wait 1-1.5 weeks), Quick Carbing (there are schedules here for X PSI day 1, X-Y PSI day 2, etc), or natural priming (Add about 2/3 of sugar that you would use in a bottled batch, seal it up, and let it sit at room temp for 2-2.5 weeks. May have to dump the first few quarter pints until the yeast clears out).