How's my equipment?

I recently got to Tier 3 (yay) and want to know whether I should try to keep upgrading my 4* equipment or switch to different alchemy lines.
I have:
Ash Tail Coat
Ash Tail Cap
Ascended Caliber
Mighty Defender
Spine Shower
Should I keep upgrading this? Or switch lines?
Also, I have an Autogun that I kind of like, but for some reason it keeps nagging me that it isn't too good. Could somebody please help me decide whether to upgrade or switch in terms of guns too?

I'm a melee fighter mostly and I use mostly swords and the bomb is for the novelty of the bomb. If I would have to go with the Haze Bomb series, I would probably start out with the poison line for JK runs and then move on to the fire and freeze lines when I get the money. Do you have any suggestions for guns?
Always, armour depends on your weapons of choice. If you primarily like to melee, then upgrade your Ash Tail to Skolver/Vog Cub. Though, Vog Cub can be arguably better generally, but I have both. I only use Skolver for stratums that need good pierce defence, though.
Calibur is a good sword to roll with, but again, it'll depend on your kind of swordplay. I am a primary sword-play kinda guy, so I roll with good DPS - I usually carry around a Glacius with either an Acheron or Barbarous Thorn Blade (I would recommend Final Flourish over BTB though). I use Glacius for its bonus elemental damage vs constructs/undead, Acheron for its shadow damage vs gremlins/jellies and BTB for its pierce damage vs beasts/fiends.
As for your shield, I would say Mighty defender is okay at best. The best well-rounded shield is probably the Grey Owlite though (mine has UV pierce high). I'd really only use Grey Owlite for Firestorm Citidael (soon to be replaced by Crest of Almire) and Swiftstrike Buckler for everything else, though.
And finally for your bomb, I wouldn't say its quite useful except for hordes of wolvers. Other than that, I wouldn't really see much use of it - I would rather roll with a haze bomb line. Shivermist Buster is probably the most popular as it can really make fights easier for your team. Ash of Agni is also very good for damage.