>>44163427I did the strategy that gets mentioned a lot in a Gen 1 hack and it worked well. I assume the Game Corner was unmodified from RB so it should still apply.
Basically pick a machine, and if after like 3-5 spins you're not getting a particularly high amount of coins, if any at all (I think it's like 25-50 or better but I don't remember offhand what the payouts are), move on to a new one. Repeat until you find one that's consistently paying out and then repeat until you have enough for the Porygon. There should be at least one machine that consistently pays out high amounts regularly. If Red's the version where Porygon's like 9999 coins then yeah, it'll take a while.
I also noticed while using this strategy that it seemed like sometimes the "good" machine would stop working as well, but it could've just been me becoming complacent and timing it shittily. In those cases I'd leave the building and then repeat the process of finding the high-paying machine again.