I really hate the guns to be honest. In the preview I went in with 4 swords equipped: Leviathan Blade, Wild Hunting Blade, Gran Faust, Avenger

I guess it's really what you prefer. I like to get up close and personal with my enemy's! >:D

I ran with 4 guns durring the preview event: Shadow Driver, Magma Driver, Sentenza, and Argent peacemaker. currently I am only running with two guns: Shadow Driver and Firotech alchemer mk II.

I have no trouble with those two guns on any mobs. Devilites can give a little trouble, but if you wait for them to attack, or just shoot till u trap them in a corner, they go down rather fast. I know alot of ppl also have touble dealing with wolvers, but I have found an easy method to take them out. I only shoot at them once they start their attack (gain red aura around them) as I back away. Also when they goto howl or bark or whatever they do, u can get a couple free shots in on them without them dodgeing.

There's not really a downside to this style of play, you can actually have an extremely well rounded loadout with just all guns.

For close range attacks, fights in tight spaces or against monsters who randomly dodge, an Autogun type weapon can replace your sword. It doesn't stop monsters from dodging, but at close range, theres no way they can get out of the way of your bullets. I'm not sure how the Volcanic Pepperbox is in it's current incarnation, but it should still be an excellent weapon for straight up ranged DPS. Since it deals Normal Damage it's equally effective on all monsters as well. You could use the Valiance for Normal Damage, but it's very plain. Using Normal Damage isn't recommended most of the time anyway, only as a last resort. The Volcanic Pepperbox makes a much better last resort weapon than the Valiance in all situations that would require it, anyway.

For elemental attacks, you have a lot of choice. The Firotech Alchemer, Voltech Alchemer, Cryotech Alchemer and Prismatech Alchemer all deal Elemental Damage amazingly well. While the Alchemers that deal a status effect can be less desirable during certain situations, like Oilers and Quicksilvers, the Prismatech Alchemer is neutral, in that it doesn't deal a status effect. This can also be a downside, as you're using one slot purely just to deal with two kinds of enemies (Constructs and Undead). I would recommend any of them, as Shadow damage is strong against Slimes and won't set any of their special effects off by accident.

The Shadowtech Alchemer is currently the only gun in the game that deals pure Shadow Damage. The Sentenza deals Shadow and Piercing damage, which makes it less effective against Slimes (but still effective on Gremlins), however because it is so fast and spammable, some people prefer it to having two Alchemers. Although I don't recommend it.

The last gun you'll need is the Callahan, which deals pure piercing damage and has an extraordinary range. Using it from long range means monsters won't dodge your charge attack bullet, this makes it very easy to take out Wolvers and Devilites. This gun's big brother, the Iron Slug, is also an excellent gun, however it deals normal damage instead of piercing. It explodes in an area of effect on hit, making it good for controlling monsters, but it also hits stationary monsters like Gun Puppies twice on a charge attack. They both stun, which slows monsters down considerably. The only real downside is that occasionally, the charge attack can stun you as well.

There is another possible set, though.

Mainly, swapping the Volcanic Pepperbox for a Blitz Needle and having the Iron Slug for normal damage instead.
Since the Blitz Needle counters Wolver and Devilite dodging quite expertly, you can use it purely to wipe them out on sight.
Keeping the Iron Slug to execute monsters from outside of their range of attack.
Either way, it's still relatively balanced.

So the best loadout for all Guns currently is:

1. Volcanic Pepperbox: Normal Damage, High DPS weapon. Chance to inflict Fire.
2. Hail Driver: Elemental Damage. Crowd Control, monster abilities can't accidentally triggered by the Freeze Status.
3. Umbra Driver: Only gun in the game that deals pure Shadow Damage.
4. Callahan: Deals the highest Piercing Damage out of all Handguns. Extreme long range attack. Chance to stun monsters.

It gives a good balance. All monster types are covered. You get three status effects, Fire, Freeze and Stun. Every range of attack is covered, from Short to Extreme Long range. There aren't any compromises, bar the chance for stun from the Callahan. But Stun is by far the least troublesome status, since you can still block while stunned and you can cure it with a Remedy pill.

Personally, I would use:

1. Iron Slug
2. Blitz Needle
3. Sentenza
4. Storm Driver

If I were to play using all guns.
Just because those weapons all look awesome and still do an excellent job of annihilating everything in your way.
It's by no means an ideal set, but if I'm going to be playing for weeks to get weapons, I want them to at least be as cool as I am.

If I had to use only two guns...
I'd use the Sentenza and Hail Driver.
Sentenza for spamming down health and the Hail Driver for crowd control.

Your armour doesn't really matter. Guns are fairly slow, so just using a Swiftstrike Buckler with some Gun Charge Time Reduction armour or Increased Gun Damage armour will do wonders. Trinkets are even better. If you want a shield that offers better defense, you won't suffer for not having high attack speed, though.

That's my enormous post on the matter.

I'm getting a Callahan aswell, I have an Iron Slug and Swiftstriker Buckler already aswell as Justifier Hat.

Justifier Coat + Swiftstrike Buckler. Callahan, Iron Slug, Argen Peacemaker or Hail Driver and Umbra Driver... This is what I'm aiming at.

Although right now I'm doing melee since it's the most efficient way to farm, timewise.