I think the best electric Pokemon is either Electabuzz or Jolteon. Both are obtainable earlier, and their stats are very similar. Pinsir and Heracross are better bug Pokemon than Galvantula. Also, I don't think Mandibuzz is good for playing the game even though it's powerful. Its relatively weak physical attack means it slows down battles, so other Pokemon like Sigilyph or Zoroark let the player finish the game faster even if they might not be as reliable.