That's some great advice! I have a friend who is an S+, and took me into a squad battle when I had just become an A. It was quite the slaughterhouse, haha. I left the battle with 20+ kills. I have never seen a messier map. These darn messy squids!
As for weapon sets, I do not play blasters. I was never able to get into it. The slower pace of fire really made me uncomfortable. Due to having no experience in that set, the range and odd active hitbox made me incredibly vulnerable. I've seen some really terrifying Luna players, though. The real problem is when they get close to you. I play chargers for the most part, but I like to take a break with the .52 Gal or .96 Gal Deco.
Now that I think about it, I need some weapon variety. I rarely use the Carbon Roller or Heavy Splatling for ranked, anymore. Do you suggest any sets for me? By mode, perhaps. Rainmaker, Tower Control, and Splat Zones?
Did you get to S+ through solo queue, squad battles, or a mixture? I tend to lose squad battles, no matter what happens, so I hang out in solo queue. Gee, man. I could learn a lot from ya! Thank you!
You're variety isn't too bad; it seems that you do well with longer ranges. The .52 Gal is pretty decent in close range too, so you don't seem to be doing too bad. I'm sure Blasters are pretty easy to take out with the .52, but you probably don't have as much luck with weapons like the Splattershot Jr. and Splash-O-Matic (these are all just assumptions, based on both my experience and the fire rate of the weapons, so I could be wrong). For dealing with Lunas, I have one big long recommendation-
Run Away.
Just Run Away.
Seriously, get outta there.
The Luna Blaster is like the COD equivalent to a shotgun- no range (well I mean that's not entirely true, but only because I'm really good with it). The best way to counter a gun that has a wide short range and deals massive damage is to stay out of that range. If one starts getting close (especially since you use weapons like chargers and the Gal variants), just fall back, and take 'em out from a distance. I'm the king when it comes to sneaking up on unsuspecting squids. But if they're attentive enough and pull out a little distance away from me, that's it. Clocked out. Done. I just can't do anything- I can maybe throw a Splat Bomb, but I'd have to be really lucky to take you out with it (and even if I do, I'd still get splatted beforehand). There's the specials too, but I don't really consider those too much into my strategy, since they're not always there (I don't really like having to rely on something I don't always have, especially since the Luna doesn't have very good ink coverage ability anyways). Splash Walls are great too, I CANNOT tell you how many times I've killed myself by swimming right into one (
thosedamnthingsaresuchbullshitandsoembarrassingthatijustwannabreakmycontrollerwhenithappens). So yeah, that's the gist for that.
For set recommendations, I can give you advice, and maybe a little insight to how I play with them, but it may or may not work well for you. Our play styles are most likely going to be pretty different- a weapon you might be good with, I might be terrible with. What I can do is run you through how good what weapons are at what, and what situations you might find the dis/advantage for any given set. I'll go through a few that I use, and add a couple more. If there's any in particular that you want advice for, just ask me (writing this stuff is pretty fun, so I don't mind).
I'll skip blasters though; You said yourself that you stay away from them, and I've pretty much given you a description of the Luna already. Now, I won't really have too too much about good pathways and places to camp with the other weapons, since I don't hardly use them (the only other weapon I'm any good with is the Tri-Slosher [not the deco], and if I'm lucky, the N'Zap. I use the Hero-Charger Replica a little too, but if I had to rank my skill with it, I'd say I'm only at an A-/A equivalent). I'm also not going to go over the Carbon Roller or the Heavy Splatling, since you've used them before, and probably have a feel for them.
Now:
Since you seem to already be pretty well off with long range weapons, and you're looking for variety, I'm gonna stick mainly to close-mid range weapons (I feel like even if I give you any advice with chargers, you'd most likely know it already). (
these pictures aren't my own, so don't ding me for stealing "such-and-such a person's" artwork)
The Slosher:

Great close-mid range weapon- it's unique firing style and ability to attack over ledges make determining its exact range during battle a little edgy. It takes two shots to splat, and has a slightly less-than-average firing range. Covering turf easy with this weapon is a breeze, so rocking skills like special charge or duration up can be pretty powerful. However, while the weapon is effective close range against other mid-long range weapons (Splattershot, Chargers, Gal variants, etc.), trying to compete in a close firefight with a Luna Blaster or Splattershot Jr. or Sploosh-O-Matic etc. will leave you regretting it. With those weapons, the little extra range comes in handy. But by far, the Slosher's best ability is that it fires in an arc, one where the ink falls straight downward after its arc (that might be worded a little wrong, but you've played the game, you know what I mean). As quirky as it may seem to be tossing ink at an enemy firing straight at you, it leaves you with some great advantages.
1. You can attack from above, without actually being above.
2. You can attack from below, even with a ledge or wall covering the enemy (it reaches over).
If you're looking for the best situation with this weapon, it'd be at Moray Towers, Tower Control. First off, Moray Towers is nothing but ups and downs. And while even with the Slosher attacking from below still isn't a great idea (with the exception of the two ramps at the middle of the two towers, where you can climb up to the other team's wall), there are many great spots where you can hit an enemy WAAYYY below you. My favorite example of this is during Tower Control. As the tower converges on the first tall platform on your side, you can easily take out everyone on that tower.
See that yellow fence on the left hand side? You can shoot through that. And guess what else? The tower has to travel directly under there for a good while. While you should still check your surroundings and make sure that no enemies are sneaking up that wall or coming in from behind, you can (relatively safely, I might add) create a wall of death for all the inklings sitting on that tower. It takes a few tries to correctly gauge out the distance of the tower as it gets close (since you can't see it well from that angle), but it is a worthwhile tactic to develop.
Naturally, I recommend that you use this weapon for Tower Control, and Splat Zones (due to it's quick ink coverage and Inkstrike special). Id imagine that it'd be good on Rainmaker as well, but don't take my word for it- I suck during Rainmaker (I mean I can manage alright SOMETIMES, but I certainly don't have any really amazing ideas or counters for that mode. My play style just doesn't compliment it well, I guess). And last but not least, the subs and specials for the two variants:
Burst Bombs work like this: If you have Damage Up and/or Ink Saver Sub, they are extremely powerful, have relatively good range and aoe, and are my worst nightmare when fighting those F'ING E-LITERS THAT THINK THEY'RE SO SPECIAL WITH THEIR THREE DAMAGE UP SKILLS. Without those skills, I've found that they are a bit of a letdown when you rely on them; they always seemed to come just short of taking out an enemy before I met my demise. There's also an exploit you can use for quicker splats with the slosher, throwing a burst bomb at an enemy and immediately following with a slosher's, um, slosh. It'll take a bit of the time it takes to splat an enemy off if you can use it well, but it was never something I was able to get any good at.
Now, the Inkstrike is great all around. It's good really for any play style or game mode, but it's not the best when it comes to saving your arse when you get flanked by enemies and such (i.e. when you activate a Bubbler and take out the entire enemy team that thought they completely had you). It's more effective for doing things like getting the enemy off of the Tower and repainting a Splat Zone, and even keeping the enemy away from the Rainmaker. I've found that splats are pretty rare with this special, but it is nonetheless effective and versatile in many maps and modes.
For the Deco:
Splash Walls are about on the same wavelength as Inkstrikes for versatility, but are much more effective in smaller corridors where the only way to go is forward (Like the sides of Walleye Warehouse or Port Mackerel). And since you use the Gals, I think you know what you can do with them pretty well.
The Kraken is, well The Kraken is, you see...
NOT MY FRIEND
But it works great! It's like a Bubbler that gives you a speed boost, but lasts a little shorter. It's also another pretty versatile weapon, but you need to be careful not to get pushed off of ledges and such by enemy fire. And if you think you'll be splatted when you come out of that mode, you can always super jump away while it's still active. I can see you using it often when a close-ranger like a Luna or Sploosh-O-Matic catches you by surprise.
I've ran my whole rank solo queue, I've never done a squad match (the few friends I do have don't have a Wii U, go figure).
WELL! I wrote wayyyy more than I thought I was going to, so I'll come back a little later with more advice on other weapons. 'Cause, well, this took a while (but it was pretty fun). I don't know if I'll do another one tonight (maybe, but leaning towards less likely), but I'll probably do another one tomorrow.