You should pick a substyle you wish to focus the character's look on, then browse through pictures of bandmen from said substyle. I'll link you one of the most popular and helpful blog posts about the substyles. It lists examples in bands.
https://homelessvisualkids.wordpress.com/2011/11/07/a-look-into-visual-kei-subgenres/
As for what you should focus on, I think it's important to note that visual kei looks are very flashy but there isn't a certain factor that makes a look "vkei". It's also important to note that bandmen don't wear their stage outfits everyday (unless it is your stylistic choice for your oc :D).
In short, I'd recommend you focused on how bandmen stylise their hair as well as how they pair it with their clothing. For example, Atsushi Sakurai's look won't be as shocking as Kozi's for example. It all depends on the substyle!
Don't hesitate to ask me if you have any questions :)).