I used to use Super Training since I hated battle grinding in the old games, however once I found out that with Pokerus and Power Items you can get 50 EVs from one horde battle, I immediately switched to that, only using Super Training for fine tuning (like if I need a guy with, say, 248 HP, 96 Atk and 164 Spd).
Gligar isn't Attack, tho. You can train ATK off of Weepinbells and Arboks from that route, though, and the Bellsprout/Ekans from Route 15, I think? North of Lumiose, where the swampy area is with the haunted house.
I also just use whatever their other EV that I'm training for raising ATK most the time, via Power Bracer. I've been called out of my horde training from Route 19 via raining on my parade far too often.