I am not very successful with Eevee. Out of 10, I ended up with 5 Jolteon, 3 Flareon, and 2 Vaporeon. And yes, changing the nickname only works once. You can change the nickname, close and restart, then evolve, it doesn't work It will work only once. I ended up with 3 Jolteons nicknamed "Rainer". Regardless of strength and weakness, I would prefer Vaporeon because of high CP and very responsive.
Speaking of battling in the gym, there are many charts out there you could use. This is just one of them. Not really effective against a level 10 Gym with alternating type stacked pokemon, but useful when a fight is one on one and type versus type battle.
It is not as straight forward as it may look. You may think that Arcanine can easily beat Lapras because fire beats ice. But Lapras is also water, and water beats fire. Exxeggutor is grass, so it should easily beat Gyarados which is water, but Gyarados is also Fying and it beats Grass. But once you became proficient with fighting like what Joel's video showed, none of these matters much anyway. And with bot, it became less useful, with endless supply of revive and potions, you can just use brute force, and revive later, then attack again.
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