What pokemon do you have? The early bug pokemon are weak, so see if you can get a Heracross, who is one of the strongest.
I would try and teach them some moves of different types. Any electric move would be good to take on Gyarados and Kingdra. Or try a Rock move, many Bugs should learn them and you get a few Rock TMs in the game.
Apart from that, yes you'll need to level up your pokemon a fair bit if you don't have any super-effective moves.