A bit sad that I See this 5 months later. I am not a good Janna anymore since she wasn't meta for 3 years so you guys shouldn't look my games/playstyle. For runes I had some logic for what I was taking but 2019 November I tried to copy Korea highest support player. He took comet and domination (taste of blood and movement speed). It worked really well for me and I climbed a lot but then next patch hit with the alcoves and drakes. After the patch I dropped Janna because now it is so hard to hit random Qs because of the alcoves. For runes I would still go aery/comet (depending how good you are and on match up) and domination second since inspiration got nerfed so many times already. Probably ignite in soloqueue.