Actually I have never used venomoth with quiver dance to beat Aya (I did a playthrough with one but this was before quiver dance was a relearner move) Though I know how good it is at beating Aya
I beat it on my bug mono run with by a Vivilion and a Butterfree, I just them up to +5 quiver dances and proceeded to murder Aya.
My recommendation is to try and set up on Muk and Tentacruel early on, neither does a lot of of damage (a icy wind from Tentacruel I think 3/4 shots Butterfree and Vivlion.....with no boosts.....)and if you paralyze them they turn into easy set up bait. That's also how i did it on my main playthrough, status everything, nasty plot up Spiritomb, and sweep. Pokemon I would recommend for this gym? Magneton good bulk and immunity to posion, Gardevoir high sp def most of Aya's pokemon are special attackers and psychic STAB along with clam mind, Venomoth probably one of the best sweepers in the game, any ground type with eq or bulldoze Ex Swampert, Donphan ( though no one uses them anymore weird), Quagsire are all good, Spiritomb used to be a personal favorite but relies to much on sleep which I refuse to use anymore; resists poison, nasty plot, sucker punch for Gengar (though it probably will get dragon tailed by dralage.....) .
For your current team I would recommend giving every single one of your pokemon Pecha berries from the department store this saves a turn from curing posion which will happen, if you are adamnt about keeping kricketune relearn it sticky web and level it to learn perish sing as it doesn't have the stats to really be used as an all out attacker in this stage of the game, try buying X speeds to counter act icy wind this makes sweeping much easier.