As my name indicates, I main the Sploosh, the Neo one to be exact. I am LVL 49 and A on the brink of A+. For a long time, I played all wrong with this weapon, charging straight in and getting splatted a lot. Eventually, I realized this weapon is all about mobility and stealth. I do not recommend Ninja Squid though as it sucks from Swim Speed. I am sure S+ players could benefit from the usual advanced abilities, like Coldblooded and Recon. I am still not good enough to really benefit from those though, so think of this as the guide for the average Sploosher.
Anyways, I have experimented with a lot of builds, and I have come to the conclusion that this weapon's gear must do two main things: (1) increase mobility and (2) result in more special usage (Krakens gotta Kraken).
Mobility is key because you need to basically press the Sploosh against your opponent to get a kill due to its deplorable range. Swim Speed Up, Run Speed Up, and Ink Resistance are your targets. I would argue Ink Resistance is especially important as you will need to get kills by jumping into an opponent's ink sometimes so you can press the Sploosh right up against them. It is also good for when you miss and need to make a quick exit. I also value Run Speed Up over Swim Speed Up as you get more bang for your buck and you will need to be laying down ink a lot to help your team.
Special usage is also critical in Ranked as the Kraken is invaluable in clearing a zone regardless of the mode. Thus, Special Saver, Special Charge Up and Special Duration are good. I like Special Saver better than Charge Up as the Sploosh tends to get splatted a lot (so Quick Respawn is also one thing you may want to consider, though I do not favor it as a main).
My current build is:
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Layered Anchor LS
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Soccer Cleats
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There are a lot of other items that will get you similar results (and I sort of lucked out with the clothing I currently have because it does not have a huge chance of rolling some of that stuff.
Other headgear to consider:
Skull Bandana
Other clothing to consider: Zapfish Satin Jacket
Krak On 528
Forge Inkilng Parka
Green Tee
White Inky Rider
Other shoes to consider:
All the gear above has either Special Saver, Special Charge Up, Run Speed, Swim Speed, or Ink Resistance as a main. They also have a higher chance of rolling one of the others or Special Duration Up or Quick Respawn. The perfect build as of now I suppose would be something like
Skull Bandana
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Krak On 528
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Soccer Cleats
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That would be one of the ugliest combinations I think the game could produce...
As you can tell, I consider Ink Resistance to be almost a necessity. Others may disagree, but I find it saves me from getting splatted a lot. I have also used Comeback some but just do not really feel like it is worth it over another main.
Let me know what you think if you play Sploosh!