The basic pattern is pretty simple and you already described it. Mon with either baby pokemons or only 1 evolution stage will require 50 for the final evolution, while mons that evolve into their third form will require 100 and the first evolution will change to 25.
I wouldn't worry about Roselia candy if I were you, we're getting boosted Roselia spawns and the shiny in 1 week when POGO Safari Zone Dortmund starts.
