I take it you're going bomber.

Presuming that you want damage output as well as support, you're probably going to want a Spine Cone and Fiery Vaporiser, in order to mix up damage types and for when you don't want to fling stuff everywhere.
You might also want to take a look at the Salt Bomb, which is actually quite a reasonable bomb; some shadow damage is traded out for a slime bonus, but the shock status you get as well makes it more worth having than the pure damage version, and stops your enemies from being knocked around so much.
Most of the other new shard bombs are harder to work with effectively, since they are liable to knock your enemies around before you start laying down your daisy chains of doom; a Vortex will help in this matter, though.
I'd suggest you go for Nitronome rather than Big Angry, Irontech or Heavy Deconstructor lines at the moment.
Vortex bombs are awesome, although difficult to get, since the Electron version is only available through Krogmo recipes and the Graviton line isn't in HoH. You should put all status bombs on your list of things to get at some point, although Shivermist should be a priority if you plan on doing mass Vanaduke runs.

You might also want Owlite as an alternative to Plate Shield. Your demo kit is good, although I'm not sure whether you'll want to go for Volcanic (which is less painful if you get hit) or Mad Bomber (better, but lower defence and status weaknesses up the wazoo). The latter is currently outdone by the Chaos set, which gives a universal bonus, so you might want Volcanic first.
Nobody ever gets Bombastic because Bombastic sucks, mainly because CTR is more important to bombers than an equivalent damage bonus. (Sorry, Bombastic!) As for Mercurial, it's a Shadow Lair armour and is thus a pain in the butt to get, not to mention that you need to have trinkets and CTR UVs up the wazoo in order to be able to max out all your stats with it equipped, which is most likely more than you can afford at this time.

Also also, you might want a utility side weapon for dealing with annoying stuff in a hurry, like Greavers or turrets. The Leviathan Blade would be a reasonable option for a bomber to use for closer quarters. Or you could use a Nova Driver or something to OHKO puppies and stuff. Valiance, Supernova and Polaris are also decent options. I'm a gunslinger, I'm biased.
(P.S. Cutter lines look cool and do actually make an okay choice against Greavers and stuff. WHB's charge has quite a bit of attack cancellation on it, too, although DVS lacks this.)

...I'm not a gunner? I do sword/bombs/guns. All of em.

Fleet-Miss-Gun, you don't seem to be advanced to the point where you need super-specialized advice. To get there, maybe answer these questions:

In PvE, do you usually play solo, in random parties, or in known parties? In PvP, do you bomb a lot?

Do you prefer to deal damage yourself, or are you more of a support bomber?

Are you going for a highly offensive loadout, or do you want to maintain a balance of offense and defense?

Have you read the Bombing Guide on the wiki? (It describes the armor sets and bombs in some detail.) Based on it, which 5-star armor and bombs are you considering? (Always plan in terms of 5-star items, because that's where everything ends up.)

Aw. So since I'm not a pure-bred, I don't have rights above everyone else? 0======
Just kidding, but I'd read Bopp's post. Also, read the bombing guide.