Get an air tank from Harbor Freight… You fill it via a Schrader valve (same as car tires), so you can charge it at any gas station. A bike-tire pump works in a pinch.
My pressure gauge is 0-30 psi and has 1/2-psi increments. The cool feature you won’t find on garden-variety gauges is the bleed valve. It’s a small button you press to release air from the tire a little bit at a time. You over-fill the tires a bit and then bleed them down to the desired pressure. I don’t remember the brand, but I got it for $30-ish at IMI.
Ditto what Troy said about testing in order to hit the optimum pressure (13 psi for MG Yellows) at the right time.