I know there is a thread about this but I wanted to make sure which is the best for me personally.
So can anyone tell me which gun and which line should it go judging by my equipments?
Prefer pulsar or catalyzer because i have some barks
Skelly Mask
Scary Skelly Suit
Nightblade
Defender
and Firotech Alchemer
If you're asking specifically about the RT guns, I'd go for the Pulsar and upgrade it into Kilowatt, which does shock and a helluvalot of knockback - enough to be flinging Trojans around even if you don't hit their backs. It's good for playing Lumber Pinball, but it will piss a lot of swordsmen over when you send one flying into their faces, and the explosions are quite large, which can be distracting.
Personally, the Catalyser is pretty lame, because the bullets don't travel fast and the charge explosions take a long time to set up. The Toxic version looks good for JK with Poison and Shadow damage, but you're likely to hit the baby jellies with the charge rather than JK itself. If you want a Shadow damage gun for JK runs, get the alchemer instead, although since you're using Nightblade...
You could really do with piercing damage in your loadout. The Antigua lines are apparently being revamped, though, wait for the outcome of this before you bother working towards Sentenza or Argent Peacemaker.
The nerf guns are made of nerf mostly. That is to say, Autogun needle lines, which will leave you stuck in place whilst firing. It's a pretty big drawback in most of the game, but they do excel against Trojans and Vanaduke when you get there. I wouldn't bother with them for now, since they're liable to get you killed if you're not too careful and aren't that great against fiends or beasts (since wolvers and devilites have the tendency to dodge as soon as you shoot near them).
Don't personally use the Magnus line, which is the last piercing line, I think. It does a whole load of knockback and more damage than Antigua but knocks you back as well, and the charge will leave you vulnerable for a bit. You might be better off finding piercing damage in the way of a sword like a Flourish.
I have never seen anyone use a Pepperbox. I suspect that the Fiery Vaporizer is the reason for this.
The various alchemers are all along much the same lines as each other, and I guess you've found out the limitations of them with regards to ricochet hitting switches, explosive blocks (and supercharging enemies in the case of the status inflict trio).
tl;dr: Get Pulsar instead of Catalyser, upgrade to Kilowatt. Also get piercing damage somehow, not the Autogun lines though.
Do not get an Antigua (i.e. Argent Peacemaker or Sentenza) right now. There is a proposal from the developers to change their damage type. Wait until that happens, before making any commitment. If they stay as they are, then do not get them; their mixed non-normal damage types make them hard to integrate into a good setup.
I agree that the piercing swords are easier to learn than the piercing guns, because the latter all have some kind of mobility problem. But serious gunners learn how to use the piercing guns, and you can too.
I just forgot to mention that I also have a flourish and crowns enough to by a 3star equipment or alchemize one.
Which should i buy/upgrade first?
Among mixed sword/gun setups, your type (piercing sword, elemental gun, shadow sword) is popular and good. Go with it. If you have just two weapon slots, then carry either (A) the piercing sword and elemental gun, or (B) the shadow sword and elemental gun, depending on the stratum/level you're entering. You can also carry the two swords and not the gun. Pure sword setups are quite common and viable. The important thing is that you have piercing, elemental, and shadow, and deploy them against the correct monsters.
I would make sure that everything is 3-star, before upgrading anything to 4-star. Other than that, the order doesn't matter much. Upgrade whatever you use most, first.
*the Catalyser is pretty lame, because the bullets don't travel fast and the charge explosions take a long time to set up.*
Huh? The projectiles may be slow, but setting up the charge really doesnt take that long, unless youre trying to do multiples.
The single most important consideration in choosing a sword or handgun is damage type. Basically, you want a piercing weapon, an elemental weapon, and a shadow weapon. Use them on the correct monsters (see the wiki page on Damage) to maximize your damage output. Right now you have a shadow sword and an elemental gun.
The best use of your Bark Modules would probably be either (A) start work on a Biohazard, or (B) give up on the Magma Driver line and switch over to Polaris. However, neither of these really complements what you already have. My recommendation is that you start work on a piercing sword (Final Flourish or Barbarous Thorn Blade), or maybe a piercing gun (Callahan, Blitz Needle, or Plague Needle), or maybe the piercing bomb (Dark Briar Barrage).