I've been making art related to a certain game called deeeep.io, which as the name suggests is about aquatic animals

the art i'm making is of a giant squid based off the individual recorded on footage back in 2012, and with it, i wanted to get that sort of metallic, reflective look it has... but I'm not exactly sure how.

I've asked for advice from people on the subreddit on how exactly i should go about achieving this metallic look, and most people have told me to try using lots of gradients, which, in a vacuum that might work, but my problem is that such a heavy use of gradients would clash with the game's artstyle, which primarily uses solid (though not necessarily opaque) colors and, if any gradients are used, they're fairly minor, simple and subtle. I'll attach a couple examples of arts I've made for this game previously.

I've also tried asking for advice amongst other people who also make art for this game, but that hasn't really helped either, since most of them haven't made any sorts metallic/reflective art themselves. There is one exception that i can think of, which I've attached as the last image (its not my art to be clear), and i think it does a great job at looking metallic without overusing gradients. However, I'm still not 100% sure on how they did it, and Im not sure how much their techniques would be applicable to what I'm making, since their design is a lot more, well, machine-y.

so yeah, if any of y'all know how i could get a metallic look without overusing gradients, I'd really appreciate that. Basically any other way to get a metallic/reflective look, like maybe transparent shapes, geometric patterns, anything really. I'd especially love any visual tips, like reference art, video tutorials, or anything else that can help me see how it all works.

Thanks for y'all's time!

Maybe you can try out filters. Here's a quick example using [Filter > Materials > 3D Mothert of Pearl]. Svg filters can be endlessly customised, but I'm no expert. I suggest perusing the many internet tutorials out there.