I think you're weak to bulky Waters, Psychics, and Bulky Grasses. You don't need to use Hippopotas as a lead, because your team doesn't really benefit sandstorm. I suggest you this:
Gligar @Lum Berry / Focus Sash
252 Atk/ 252 Spe
Jolly Nature
Hyper Cutter
-Earthquake
-Stealth Rock
-Stone...