Twirl Skirt gathering problem/question/issue

Sigh...
Ok. I think that I'm truly dense. I'm trying to make a patchwork twirl skirt for my youngest daughter.

I'm having a hard time gathering the layers and putting it together with the layer above. (I am manually gathering as I do not have a gathering or ruffle foot).

My problem is that I don't know exactly how much to gather it. It gathers well. Here is what I have, layer-wise.

1st layer = 9 squares
2nd layer = 14 squares
3rd layer = 21 squares

How do you gather it to where it fits the above layer? I'm so frustrated.

Is there some kind of formula? Like each square should be 2/3 the size of it's original size? and 3 gathered squares should fit 2 original squares in the above layer? (got that from the twirl skirt (toys for tots) pdf on YCMT. <~~ I do have these instructions. I've read them like 8x already. Sigh!

My squares are 4 x 4.

Do you divide 1st layer by 2nd layer and so forth? i.e. 9/14
of 2nd layer by 1st layer? i.e. 14/9

ARGH!
Sigh..my head hurts trying to do this.

Any help will be appreciated.