Hello, welcome to PRO.
I suggest not to evolve your Pokemon till it is 96+ level. Since evolving it early on will just make it harder to level up. Keep it in the first stage till it is level 96-97 or more depending on the Pokemon. However, this is with the exception of Happiny, Blissey and Chansey. They all are different evolutionary stages but still require the same amount of EXP to level up.