If you find yourself in a situation where you're fighting on multiple fronts with a single army so early on, just restart a campaign and try again. It's basically a dead start. But if you want to try and recover, the only option I see is making an army with a few cheap units to safeguard the settlements from VC sacking them, while using your other army to bully dark elves and whoever else is at war with you until they ask for peace or you wipe them out. Expand your economy and get two armies of decent units (Saurus, feral cold ones, some feral stegadons) then sail for Count Noctis's capital and wipe them out.

From there it should be smooth sailing. But if I was in your position I'd seriously just reset, your situation sounds hopeless, being at war with more than a single faction with only a single army is a recipe for a really bad time.

Remember to build a geomantic pylon ASAP, and upgrade it as soon as you can, lets you fly through your own territory. Also something I do alot vs other people is to build a scrying pool in provinces I know there will be lots of fighting as it nerfs their movement speed if they start their turn in province.

Outside of that can't go wrong with getting a skink priest fairly early and trying to power level em in one of your armies as a blocker. Or if you see an army coming to hit a specific region just try to be in ambush nearby, even if you don't get him on the ambush you'll prob be able to catch him the next turn.