Don't worry, you haven't messed up anything. The delicate flower quest can be attempted as many times as you want. You can try it again right now or come back much later when you've got more upgrades and charms. This game is designed to play in whatever order you like. The only true limits are areas that require specific abilities to access, the rest depends on your skill and determination. There is probably an optimal route, but I certainly didn't find it, as I was all over the place in my playthrough. It doesn't matter in the end though.
I don't think I've ever specifically grinded for geo, except at the end to get the unbreakable charms. I did the Trial of the Conquerer over and over for that, but that's pretty much endgame. I don't know where you've been already. The Great Husk Sentries (large guard type enemies) in east City of Tears (near King's Station) give a good deal of geo, but they're tough bastards and deal double damage. If you haven't been there yet or don't want to fight them, I believe the Moss Knights in Greenpath also give decent geo.
You're not going to get thousands of geo fast like this, but every time you get a couple of hundred there's probably something you can spend it on. Don't try to save up too much to spend at once, just go spend whatever you can when you can.
