Some people have asked for clarification on this, so let me go through these things one by one:
Raw meat - Inklings are omnivores. While their squid ancestors ate raw fish and crustaceans, they’ve evolved beyond that. They must be fed a varied diet of fresh seafood, fruit, vegetables and carbohydrates. Inklings can eat many of the same things humans can and each has their own preferences. They are very active creatures and their caloric needs are often above what a human of the same age would need so keep this in mind. Be wary of pellet diets for Inklings as well. Even if nutritionally complete, they are bland and most Inklings refuse them. Would you want to eat pellets?
Water - Though Inklings can drink water like most living things, their chemical makeup means it is unsafe for them to be submerged or deluged with water suddenly. This will “splat” your Inkling, and unless you own a respawn pad (which you should) you’re looking at a long and unfun recovery for your squid.
Paint and ink cartridges - A healthy Inkling can make all the ink they need. While an Inkling may enjoy having art supplies, they aren’t necessary for them to turf with. It is a complete misconception that Inklings use paint to fight.
Foam rollers and squirt gun - These are a complete joke, the equivalent of giving your dog a cheap stuffed animal they’ll tear apart in 2 seconds. Only appropriate to give a very young Inkling too little to use proper turf weapons. Inklings need a variety of weapons for enrichment, including full-sized rollers, shooters, chargers, etc. If you can’t afford at least 4 or 5 weapons for your Inkling at minimum, you should not have one.
Cage - I shouldn’t have to say it, but you should under no circumstances attempt to cage your Inkling. Not only can they easily escape by slipping through the bars, it’s completely inappropriate to cage a creature with the intelligence of an adolescent human. It is perfectly safe to give your Inkling the run of the house as long as you set boundaries for them and don’t leave out anything you mind being broken or inked on.
Toy phone - Inklings are social, so even if you have two (and you should, especially if there are no other Inklings nearby they can have playdates and turf wars with) they have an innate need to keep in contact with others. An Inkling will be bored with a toy phone immediately and feel isolated, leading to depression.
Kiddie pool - Far too small to be used as a turf arena. If possible, consider converting your entire backyard into a turf war course, or have a skatepark or industrial site nearby they can use. This is essential, Inklings must have a place, ideally several places, to run around in.
Outfits - Inklings love fashion and need to be able to express themselves through it. They should have a variety of clothes to mix and match, as many as any human teenager. You should let your Inkling pick their own clothes and take them shopping at least monthly. They need not just shirts and pants, but shoes, jackets, hats and accessories. While two outfits may be sufficient to keep your Inkling clean and clothed, it stifles their creativity, again leading to depression or even aggression.
Music - Like fashion, Inklings thrive on music. Dancing is one of their favorite ways to keep active. If you live in an apartment, a pair of sturdy headphones will suffice to keep them quiet. It is recommended to take your Inkling to at least one concert yearly. Not allowing an Inkling to listen to music is simply cruel.
Math - Don’t make Inklings do math, they’re stupid :(
On a similar note, though they are physiologically similar, Inklings and Octolings have distinct needs. Octolings on a whole tend to be more shy and calmer than Inklings, so keep this in mind if you are considering adopting one as a companion for your Inkling.