I've never lost against them, playing Hordes and Cult. KE definitely has a shallower learning curve than some of the others, but all factions are viable. Like Retnab said, with GH use cover/pools to your advantage, and bring Whelks if you have them. Storm Siren has an amazing Lure, which you can use to bring the food closer to your fishes.
For non faction specific advice, remember that you win games by scoring points. Excluding Pitched Assault, it tends to be very difficult to score points if you don't leave your deployment zone. Casualties are acceptable (especially if you play Hordes) if it means you are scoring