I'm fairly new to Gremlins myself, but have been rather successful with them here in the early going. Obviously I'm not the definitive source, but maybe what I'm fielding can help you out.
I'm currently 3-1-2 in the 6 actual games I've played. There were some test games in there that I don't count because we weren't using scenarios and schemes, which basically means we weren't playing the game. That really should be 4-1-1, but there was some confusion in a game and we called it a tie.
I use Somer pretty exclusively. I used Ofelia once for an Achievement Tournament, and while I was sucessful in that game, I didn't like the way she played. She's far too aggressive, and I've found if you try to go toe to toe with something like Neverborn you're going to get chewed alive. While I am looking forward to playing with Ofelia more, especially once I have her entire warband in plastic, I'm staying away from her until I'm more comfortable with the game and models.
In our area, we've been playing at 45 Soul Stones. I'm fielding Somer, 4 Bayou Gremlins, 4 Piglets, a War Pig, and a Hog Whisperer. With Somer, I field the upgrades Can of Beans, and Pig Feed. This allows me to more or less cover the board with models, and the 2 models with the 8" Pork Whispering Rule allows me to keep the piglets and War Pig in line. The Piglets are my stars. At Def 6, and having the Small special rule, they are perfect for pushing the field quickly and setting scheme markers. It's hard to shoot them, and you can keep them far enough from the Hog Whisperer to stop things from shooting him. The 1 action charge is also really nice, because Master's that have Defensive Push triggers can't run from the initial charge, they will simply get charged again with the second action. (Please let me know if there is a rule against charging twice, looking through the rules I can't find it.)
Just a side note, I said that in my experience going toe to toe with some warbands will get you chewed to bits, I'm sure there is a way to make Gremlins into a beaty type warband. In fact, Ofelia's crew is really good, and there are plenty of good, tough models. I don't see a reason to do this, especially when the game is truly won and lost on the backs of Objectives. Not saying it can't be done, I just don't find it optimal.
~J