Crafting can be confusing, yes. SO much information, so many details! That information hidden is on this page (and on others), but I'll explain it.
When you make a weapon, the "enchantment bonus" (+1, +2, etc.) is automatically applied. Same with Spell Casting Impliment Bonus (SCI), BUT you have to have some spell-related effect crafted on the weapon! No spell effect = no spell casting bonus.
An augment would give you a boost to that type of spellpower, but still no SCI bonus, as it's not part of the crafting. Red/rubies:
Now - you can put a spell-related effect on several other items (and the Wiki implies those any "item" will work), but I'm not sure if all of those will give you the same SCI bonus - spec. gloves, necklaces, rings, trinkets, armor, and shields (and rune arms).
So - if you can make one of your two weapons "radiance" or "devotion" (or the lore version, or whatever) - there's your SCI bonus. If you can craft it, best might be to add an "insightful X power"* - gets the SCI without much DPS loss, esp if it's on the off-hand. Otherwise, just a weapon enchantment bonus, sorry.
(* Note that "Insightful Spell Power" goes in the suffix crafting slot, not requiring the "extra" slot.)