Looks like you skipped a boss to me.

Before heading to the plains, you should have gone to the mountains first to get Silver and wolf pelts for better armour and weapons.
Only with those you stand a better chance against the Furlings (or goblins, as you call them).

Once you have established yourself a base in the mountains and have defeated Moder - the 4th boss - I suggest you make sure you have gathered enough materials - and especially the food items, before exploring for the plains.

Only tip I can give you to that,

try to find a spot where Plains border Meadows or Black Forest.
Set up a camp there, make sure it has a portal connected to your main base, and slowly start exploring the plains.
If you manage to lure the Furlings in small numbers to you, hit them with as many arrows as possible to "soften them up", you do stand a chance against them.
Once you got the metal found in the plains you will be able to craft better armour and weapons, making surviving there a lot easier.

Thorin :)