Upgrade?

Definitely wait for some reason

Wait for a good Porygon. That Pokedex can wait

Unless you feel a pressing need to use it as an attacker/defender for some reason, I would wait until the next time you do a mass evolve with a lucky egg, if you do such things periodically

Congratulations on having 50 candies. My first special item was upgrade and I am short of candies. That said, I will evolve the first lucky egg I use after getting Porygon candy # 50

I just got the Upgrade Item from the 7 day streak and evolved one, why wait when I can get a new Pokedex entry and sit on shitloads of Porygon candy (They were quite common here during the Valentine event and I really feel sorry for the poster above)