I've been considering making a new character, redoing MB, but doing it right.
It goes a little somethin' like this.
MB Theory
Magic Bullet - 4.85 (18k Expertise used)
Shot - C6.5
Gun Knowledge - C5.5
Curse - C5
Magic Control - C1
Sharpshooter - 4.5 (2k more Expertise used)
Shot - C6.5
Gun Knowledge - C5.5
Demon - C2
Retaliation - 1.2 (4k more Expertise used)
Attack - C2
WK - C1
ST - C1
Curse of the Wretched - 3.0 (2k more Expertise used)
Destruction Magic - C1
Curse Magic - C5
Magic Control - C1
Bless - C1
Total of 26k Expertise, build can only be completed at level 90.
This is my ultimate MB build, something I've spent a little bit of time putting together. Essentially, it comes out to a "Jikokuten-Killer", as it grants the user Scorching Bullethole and the corresponding SS toggle for Jiko. But I'll go into detail about why what expertise is where.
I initially wanted Gun Knowledge to be as high as possible, but sadly, trying to fit as many damage-increasing chains into this build, I had very little wiggle room. Shot and GK are where they are to ensure that MB and SS are at acceptable levels.
I needed Curse at its max level to give the easiest boost to COTW, giving me access to the 3.0 Skills.
Essentially this build is capable of dealing most of MB's elemental damage, only being short 2 elemental shots. I plan to overcome this shortcoming by having corresponding elemental guns and using Arm Snipe with them. This build also has 4.5 Sharpshooter, granting access to most every toggle you could want for PvE combat, giving you the ability to do extra damage to Guardians such as the 4 Kings. Along with that, this build comes equipped with 1.2 Retaliation, essentially giving the MB the ability to abuse the Dying Hres SS combo (+30% affinity damage, +50% general Long Range damage). As such, this gunner will HAVE to be Law for this to make any sense. Finally, this build is equipped with Class 3.0 COTW, granting access to the various damage-increasing hexes, namely, Bullet Hex. With the combination of the enemy's elemental weakness, their corresponding SS toggle, Dying Hres activated, and Bullet Hex landing, this build ensures MAX damage against any one enemy at any time.