Janna tips

Hi I'm plat player and happily climbing in silver to gold promos

Could anyone offer me some advice on what runes you should run on Janna And what items you run on her like I don't know what I'm building half the time I keep buying Mejais whenever I can since my team keeps snowballing every game.

That 6-0 win streak using Janna must be a sign Lol so decided to main Janna now lol