I can't say anything about the technical side of setting up a groupbuy, I can't offer any advice on that, I apologize.
However I would like to offer some suggestions on the design.
I think you should get rid of the Japanese sub characters on the keycaps. Japanese characters are really common and it's starting to get to the point where some people are avoiding keycap sets with them in it because other sets do it better.
I would also suggest making the backslash red since in that row, seeing one purple keycap throws off the composition.
Overall, I love the set! There's good attention to detail with the modifiers being red/blue and the actual letters being purple. It's a really nice touch
If this ever made it to GB I'd 100% go for it.