if you were only gonna do one thing, make it, upgrade to the PA50ii ramp plate.
if you can do two things make it, the PA50ii ramp plate and add a custom exhaust pipe
if you can do three things, make it the ramp and the exhaust and try to drill out and jet your carb or its easier to just replace your carb with a PA50ii carb or PA50ii clone carb.
if you can do four things, make it the ramp plate, the exhaust, the carb and replace your 1reed valve and intake combo with a PA50ii 2reed valve and intake combo (or the 2reed valve and just use your stock intake but port and shape the daylights out of it til its a match for the 2reed valve)
if you can do five things, make it the ramp plate, the exhaust, the carb, the 2reed valve and intake and swap your PA50i cylinder for a PA50ii cylinder or a kit cylinder.
others may argue about the best 'order' to do them.