Starting engine for the first time...oil pressure

Well I went to Walmart to buy some more oil and found a little $6 mechanical oil pressure guage (designed to fit under your dash). I plugged that in and was able to get 50-75psi with my cordless drill depending on speed. Not sure what I did but everything seems to be working now... Just have to tie up some loose wiring and I am ready to start it for the first time! Thanks