The Janna build for Support is Shurelya's Battlesong and Summon Aery. This LoL Janna guide for Support at Platinum+ on 13.24 includes runes, items, skill order, and counters.
Janna Counters
Jannawinslane against...
Win Rate
Matchup Rate
Alistar
2494 games
2.3%
Rell
2636 games
2.4%
Shaco
806 games
0.7%
Leona
2684 games
2.5%
Braum
1232 games
1.1%
Rakan
6212 games
5.7%
Milio
3194 games
3.0%
Jannaloseslane against...
Senna
7250 games
6.7%
Xerath
2662 games
Vel'Koz
1202 games
Zyra
3477 games
3.2%
Neeko
1076 games
1.0%
Brand
1877 games
1.7%
Lux
4877 games
4.5%
Zilean
1624 games
1.5%
Pyke
3756 games
3.5%
Swain
1550 games
1.4%
Ashe
2730 games
Morgana
2931 games
2.7%
Pantheon
738 games
Karma
3103 games
2.9%
Seraphine
1836 games
Yuumi
2181 games
2.0%
Bard
3504 games
Sona
1958 games
1.8%
Taric
755 games
Thresh
7324 games
6.8%
Nami
4120 games
3.8%
Blitzcrank
3974 games
3.7%
Lulu
4347 games
4.0%
Soraka
3377 games
3.1%
Nautilus
5078 games
4.7%
Maokai
1040 games
Renata Glasc
3220 games