Um yeah just basically how I do my eyes, step by step.
Step 1 Draw lines. Step 2 Color the eye. Step 3 New layer, clip to first layer, set to multiply, draw in iris. Step 4 New layer, clip to first layer, set to multiply, draw a darker version of the iris closer to the bottom of eye. Use same color as eye color. Step 5 New layer, clipped, set to linear dodge add (luminosity for sai), draw circles for small highlights. Use same color as eye color. Step 6 New layer, clipped, set to linear dodge add again, draw smaller circles on previous highlights for shine. With white. Step 7 New layer, clipped, same settings as previous step, add sparkles! With white. Step 8 Right now, you should have 6 clipped layers. If you don't, find out what's wrong. Above the third layer, make new layer, still clipped, set to overlay, use a more saturated and lighter color than the eye color. Draw at bottom and top of the eye for glow. Step 9 New layer above lining, use white, draw some lines like what i did to do some final highlighting. Step 10 Use color a little darker than the darkest color you've used so far on the eyes. Color lines with your new color. Optional: Add a more brighter color at the top left of the eye and blend it.
Wow, lots of text. I'm horrible at explaining, so ask me if you're confused about something. Basically, the text is just useless things except that it tells you what to clip and the color and the layer mode. Derps.
Note, use this tutorial as a reference to generate a new style for yourself, please don't directly copy my style ok! It's not here for you to do that. I'd like to have my eye style be original.
Also, I did this in Photoshop, but I know it will work in SAI. Other programs I'm not so sure of.
I love this style, I love the galaxy feel it gets (for me anyway) after step six. It's beautiful and goes well into your style. Personally, for me, I really love it at six, it feels a bit excessive after that; however, I still really like the eye even after step six and it looks really good with your style. It might just seem excessive here simply because it's on its own and not on a full drawing of a character.