Need help modding custom sovereign equipment

I'd like to add more equipment options to the custom sovereign creation. For example a better weapon of each type, worth 1 point. I want to make use of the existing equipment that is already in the game, so I'd like to have the weapons from the Enchantements technology selectable. I haven't really modded anything so far and have no clue where to start. Can someone point me in the right direction please? Is this mod even possible and what files do I have to edit?