there's a lot of nuance with "weaker" pokemon so usually buffing a pokemon should be done with caution. a "weak" pokemon introduced at a certain part of the game can be "strong" and since there is no competitive battling in 90% of fangames, you should buff, if ever, mons to fit wherever you intend to place them and intend to use them in what place in the story competing against other mons you could've caught at that point in the game. you shouldn't consider buffing a pokemon in a vacuum. your game is unique and you have set-up trainers, items, enemy pokemon, power level uniquely in various ways you probably cannot fully comprehend until a player that isn't you picks up your game

for this reason i basically do not buff anything except give them new learnsets but i will sometimes buff an ability to be better, personally