You may not have the issue anymore, but what I did was wait until I got my first gnomads to set up a military, and I used three of the four gnomads for my squad. I had already built a training grounds near my front door, so I set them to train from the moment I got them. Their fighting skills improve phenomenally in a short time, and any enemies that come near will automatically be attacked.
I rushed a butcher shop and bonecarver and killed my male yak as soon as they were built. Next, I built a loom and a tailor shop, so I could replenish my bandages, since you start with so few, and I've had too many gnomes bleed out in the first seasons.
As soon as you get your armor/weapon forging set up, deck your squad out in full kit. Use whatever you can get, you can replace it later. I like the guard and shield wall perks, because they help keep your squaddies alive. Build whatever kind of military you like, but shields will likely be essential early on. Gnomes will use them as weapons as often as not, and I've had a copper shield become legendary from bashing so many throats. Also, keep in mind that you need to forge two boots, gauntlets, greaves, and pauldrons for each gnome. I'd assumed they were made as a set, but then I had a bunch of one-booted gnomes running around.
If you have an issue with invaders getting into your base, build a wall around it, and (if you don't want to completely wall in), make a well-lit entrance corridor with a few sets of doors. Add traps, if you've got them. You'll always know where they'll be coming from, and you'll usually get plenty of warning while they're knocking down your doors.
Good luck, and have fun!