This is a fun design to crochet!
I’ve used several different thread sizes as mentioned below.

Materials
Size 10: 970 yards.
Hook size 5 / 1.90 mm
32 inches point to point.

Gradient thread #2: 236g using size 2.5mm hook. Measures 38.5 inches.

3/2 thread (approx size 3) : 17 oz and a size 3mm hook

Topper worked in 49 rounds of written instructions/no symbols.

Special Stitches
Treble Crochet
Front post single crochet
Front post treble crochet
DC Cluster
2-TR Cluster
3-TR Cluster
Small Picot
Large Picot
Popcorn