What other weapons do you have? For example, if you don't have any shadow guns, then maybe you should get the shadow blaster.

For what loadout are you intending this blaster? A Firestorm Citadel loadout, where it is paired with an elemental sword? Then maybe it should be piercing (for trojans and Vanaduke's body) or elemental (if you really want to use it against zombies). A Dreams and Nightmares loadout? What?

In the end, blasters are reliable weapons: easy to use, consistent damage, no weird mechanics, a small but pleasant amount of knockback. But they're really boring, even on the charge attacks, and they don't do an especially large amount of damage.

So get a blaster, just because trying weapon styles is much of the fun of this game. But you might not use your blaster for extended periods of time, because you'll end up wanting something powerful and fun. Therefore maybe it doesn't matter much, which one you get.

The Shadow or Peirce blasters are both good.

Most enemies weak to elemental are slow which leaves them open to more powerful weapon charge attacks (alchemers)

Shadow weak monsters are kind of mixed, gremlins can be dodgy and slimes have decent speed.

Pierce weak monsters tend to dodge most gunfire but you can give them a hard tap with this gun when you need to.

The Valiance is good all around and decent in most situations, good to have when you don't know what you're up against.

In the end you can make all of them. Riftlocker I've found is less useful to use than a callahan or a blitz needle, seeing as their bullets move fast enough to catch dodging enemies off guard whereas blast shots don't. If you're more a move and bait sort of shooter, riftlocker will do you well.

If you're looking for a reliable source of damage in-between sword hits, to hit buttons, etc, then I'd recommend arcana. If you want a mobile pierce blaster, go down that route. If you want to see how enemies react to a pierce blaster, play around with a 2* one against tier 3 fiends and beasts. The bullet pattern doesn't really change with level, so if you can bait them into hits get that, and if you get too annoyed by them take an arcana.

I have obsidian edge, voltedge, combuster, blitz needle, final flourish, gran faust, sentenza, polaris, warmaster rocket hammer, and storm driver. (My 5* weps)

Then Fehzor's idea of getting the piercing blaster seems good. But in that case you might as well just get Callahan. Or even Iron Slug.

Boneblinder's idea of getting the shadow blaster is reasonable, but maybe you should just get Umbra Driver. Or Winter Grave or Grim Repeater.

To be honest my advice is to get some bombs.

I have an arcana and i seem to click faster than it fires, and if a lag a little bit it charges and I can't fire. So, I have to shield cancel most of the time and I would like to use a winter grave, Callahan, or alchemers. I say shadow, I love the huge bullets tho.

If you are planning to fight Vanaduke, get the Riftlocker, (if your main problem is Slag Walkers in Vanaduke, get Arcana,) or if you are planning on getting loads of crowns, get either the Phantamos for Sovereign Slime, or stick with the Riftlocker, for Snarbolax. Or, if you are going for Arcade, get either the Valience or the Arcana. I find Elemental is quite useful in arcade, usually.