Please try this: (Use Superior Alchemy)

Iron Net Boots + Iron Net Boots + Wolf Tooth + Vertical Wing = Skull Long Spear or Perfect Long Spear

Skull Long Spear + Propeller
or
Perfect Long Spear + Vertical Wing

Both will give out Goblin Halberd

But, remember one thing, is that the formula of Goblin Harberd is Iron + Wood. And many items also have the formula Iron + Wood. So, it may give you another items with the same formula like Sharp Katana(R23 Iron), Katana(R22 Iron), Rip Iron Sword(R24 Iron) or even lower, like perfect spear (R17 Iron), etc.

Because of this, you may have to try many times to get it.

Sorry for my horrible English