Gacha farming can get you Elephant Tusks, and many other items, with different enchants than their default. I've had Griffin Feathers with Spell-Engraven dropped from gacha coins. And elephant Tusks with Low Ether. All sorts of enchants on things that normally don't get them. Chests rewards can also do this, but gacha coins are much faster once you have a Merchant Breeding Farm. Love your setup.
Something to note with fast cast, if you're using spear, the charged spear skill will trigger fast cast insanely well. With level 3 fast cast, a single charged spear nearly fully cooled down my cyclone with skill fighter.
I'm absolutely going to try changing my build to allow for faster casting now that I have seen how fast it can go. Right now, my setup gives me 10 300 MATK and I use a lot of buffs to increase my damage. The problem with using buffs is that they have long cool down periods.
Idk if going dual wield to get "as much magic attack possible" makes sense. There's a skill damage penalty for going dual wield, it applies to most skills, magic abilities included. Only point in dualwield here imo is to proc fast cast at a faster rate.