Single R arcana Bahamut
Bahamut - Lv.120
Simple and strong. Not made for speed running
You need to carefully maintain your R buff. It's your primary damage source. The buff works like a DPS aura. You can maintain or using this buff easier by using Ashara Boots, Dragonfly trinket or Iron Treads of Destruction.
For combat, you don't have to use W to trigger R1 all the time. Just use it when you meet a tanky enemies to nuke them.
Eye of Seasons is a must-have helm for this build (see R3).
Gloves can be either Master Gloves double R3 or Grand Arcanist. One gives more BAD% and R3 to fuel the damage, while the other gives BAD% and elemental %. Both ended up has similar impact.
As for boots and trinket choice, this depends on what your other item slot purpose is. If you use Trinket as defense, then go use Boots for some more offense, and vice versa. In this build for example: I'm using Justice Greaves as a defensive item, so i use Aquastone Ring to further boost my damage output.
Weapon choices are vast. It's not on the matter of what weapon type you pick, but what rolls it has on it. Try to get one with at least BAD% + R3, and you should be fine.
I recommend rolling 2 lines of max HP on helm slot, and the rest with BAD%. That is one way to get most damage output while still having some survivability.
There are many trinket choices, such as Aqua Lily, Sapphire Lotus, Nobility Ring, etc. But i'm using the Aquastone Ring here because it's an underrated item.
~25 mins Sea, ~14-15 mins Winterblight 3. Could be shorter and faster, i'm not a speedruner. So you can do better than me.