Make the neon colors scarcer so they would pop out better, use similar colors near each other so it doesn't look messy, I would consider adding small details. btw i made a version of your mincraft skin drive.google.com/file/d/18C7t_pGg9idbVlG21OKT2LDbTAFRL-n-/view?usp=sharing

I think your skin looks fine.

I guess you can try to add some hair on the side and top. Not a lot, though. Maybe a tiny bit to make it look like the hair is coming out from under the headphones ( Or whatever it is. Forgot the name :P ). Also you can make the green more gray and darker to match the rest of the clothing.

First off tone down the black and green. Right now it's more edgy than outfit. Go with more/lighter hues of green and mix them for more variation. Check out art of black dragons from Dungeons & Dragons & Chrysalis from My Little Pony:Friendship Is Magic to see what I mean. Look at official Wizards of the Coast art in the case of the former and Andy Price's depictions of the later to see what I mean by subtle tonal shifts. Same with your hair. Purple is great-it doesn't show it but my character's hair is purple-but you want to add in some darker tones along the edges and at the root and some lighter tones in the middle. Think about where the light falls on your hair and where you'd see more color vs reflected light.

That's really the big stuff. The only other suggestion I could make is to maybe not go with a full body suit-style look or at least add some black knee pads with grey accents and a belt. Little things like elbow pad lines and the top of some boots to add more visually interesting elements. This will help make it more interesting and get rid of that 2-D look.

Try hue shifting.