These look great! Those last ones are especially awesome.
Pro-tip, you can replace the rubber band with green floral wire.
I used floral wire, and left the paper on. According to Amazon this is what I ordered. I thought it was cheaper, but that's probably because it was two years ago.
For length, I wrapped the wire around a 6" pot until the wire mass was about as wide as my thumb, then slid it off and cut it at an arbitrary point to make the individual wire lengths - I couldn't tell you how many individual wires were in there.
I took the technique from this channel. The tree in the video is pretty huge for a gaming table but its not hard to scale it down from there. That channel has lots of beautiful tree crafting vids.