The player can get up to 126 species total in Japanese Blue without trading. Without evolving any Pokémon, and only collecting evolutionary stages that the player can get in the wild / as a gift or purchase / as an in-game trade, the player can get up to 103 species. The Pokémon unavailable without evolving are as follows:
In Blue, the player can receive a Golem and a Gengar via trade; they evolve after being traded to the player. Since the player is not responsible for initiating their evolution, some may choose to consider these "acceptable" in a no-evo run - I would, since my personal philosophy is a little more like "Black/White 2 Habitat List" than strictly "no evolution". If they are counted, the number of species is 101.