There isn't a lot of planning to do when facing the plains level enemy in 2 pieces of iron. This is where you run away, using terrain to confuse them until you can crouch/hide and they get bored and leave.

That also means that your building site may be in a bad location. I would never build next to the plains, the stuff there does too much damage to structures. A single mosquito can peel the roof of a home in just a min or two. And a raging lox can flatten the whole building in seconds if you used wood.

So.. a plan?
you need more iron. A LOT more iron: it is used in the next armor sets, not just its own level set, and its used in building construction and upgrades and boats and more. So your plan for now would be to recover your body and return to the swamp or find a bigger swamp and go into iron processing overdrive for a bit. Once you have a full set of armor, you can venture to the mountains and start to work there; focus on killing some wolves first off, so you can get a cold proof cloak and a new food (wolf skewers, you need to find onion in chests there too). Stock on on the materials from the mountains (food, arrows (obsidian and cold), and if you can find some, silver). Generally you just have to take it slow in new areas. Get on the edge, see what the enemy are like, what they can do. Get some new material and figure out how to farm more of it. Stock up, upgrade, venture deeper.