Did a test with gathering. I did not use ideal fabric/needle. It was knit and I had a sharp non-ballpoint needle in, and I wonder if those effected my results.

Anyway, I tested the gather technique and ratio of tier to tier. I tried tier differences of:

• ½
• 1/3
• ¼

All tiers were 5" high. 

I didn’t complete all tier differences, because I didn’t like the feel that anything below ½ gathering felt. (like tier 1 is 10", the next is 20", etc) This might change if the total length of the fabric is greater than my small sizing (numbers ranged from 6" to 20") 

I also found that, with this ½ difference, the curve on subsequent tiers become very great. The final piece ended up three tiers, 5, 10 and 20 inches long each. The hem of tier 3 had a great curve to it. I thin this is why the original skirt has each tier slightly shorter than the one above it. (like tier 1 is 6", the next is 5", etc) 

Gathering method I used was the zig-zag and floss method. I used embroidery floss since I couldn’t find dental floss quick enough. This technique works pretty well.

Other challenges: 

When sewing the tiers together, the sewing foot kept getting stuck and flattening my gathering. This may attributed to the fabric and needle type. Proposed fixes if the fabric/needle combo is not the fix: 

• hand basting the tiers together
• hand tacking the tiers together in various locations around the skirt. 
• reduce the tier difference to 1/3