Horsea >> Seadra >> Kingdra
Evolving a Horsea into a Seadra (50 candy) may not seem like a favorable prospect at the moment, given Seadra’s less than stellar stats. Gen 2 brings us Kingdra, a mighty Water/Dragon type Pokemon, with good all around stats.
As with other Pokemon with two evolutions in Gen 1, a Seadra to Kingdra evolution costs 100 Horsea candy and a Dragon Scale (special Item).
Scyther >> Scizor
The first time I caught one, he looked so bad-ass that I thought he’ll become one of my go to Pokemon at Gyms. Alas, the Bug type Pokemon didn’t offer much, and was left in the obscurity of my Pokedex. Scyther’s Gen 2 evolution Scizor, a Bug/Steel type Pokemon should have much better stats, especially defensively, and also be immune to poison.
Like with Onix, and other one evolution pokemon, Scyther to Scizor evolution costs 50 Scyther candy with the addition of a Metal Coat (special item).
Eevee >> Espeon and Umbreon
This has got to be one of THE favorite Pokemon in Pokemon GO. The number of Vaporeons guarding Gyms is only one indication of its massive popularity. Costing only 25 Eevee candy to evolve, you can have all 3 types of Gen 1 Eeveelutions (Vaporeon, Flareon and Jolteon) fairly quickly.
Gen 2 will bring Espoen (Psychic) and Umbreon (Dark) into the mix. It’s safe to assume that they will also be 25 Eevee candy evolutions, so better stack up at least 50 Eevee candy if you want both.
Want to manipulate Eevee into evolving to Umbreon and Espeon? No problem.
For Umbreon nickname your Eevee > Tamao
For Espeon nickname your Eevee > Sakura