I need to know what I need to level up to use two-handed weapons, because I have the Gargoyle's Halberd and it says "unable to wield this weapon effectively with present stats".
If you bring up the weapon in your inventory and press the "Toggle Display" key, you can bring up a screen that shows you the details of the weapon.
The required stats are visible on this screen under the "ReqParam" header. Stats showing up in red are ones that your character doesn't qualify for.
Note that you need the full amount of Strength listed if you want to be able to wield the weapon effectively in one hand, but only half if you want to two-hand it.
The Gargoyle's Halberd requires 16 Strength and 12 Dexterity to wield one-handed.