You can use any wire you have. Large diameter wire will be more difficult to manipulate, but will increase the rigidity of the product You can combine colors and beads sizes as you like.

In the video I use for the ring 1.5cm in diameter : 20 gauge ( wire diameter 0,8mm ) : 25cm (10 inch) Wire length = number of circle rings x ring circumference + 10cm Zelenskyy: Russia massing ...