Okay, that's interesting. As you already said, Jack-in-the-pulpit and Water Speedwell are totally okay. Rainbow Rose and Crinum are to notch too.

•East Asian Eurya is interesting as very specific Magic user support. I could recommand but later.
•Adenium was solid in the past but she suffer from being an evade girl pre-rework (like 99% of 5* evade girls...). Still not that bad.
•Butterfly Bush is decent too. Not awesome but better than nothing.
•Tiger's Claw is an okay support, even as 5*.
•Harujion is kinda meh but she may be a choice if you want speed. Crit buff is still good though.
•Spring Star too for the crit. But it's better to wait her school version reprint event. She was an event 6* and she is just awesome. I guess she will be available in the reprint event girl shop for a lot of reprint crystals. She should be here in two weeks.
•Four O'Clock and China Root if you want counter+crit. Counter is awesome mid game when nothing can kill you but fail later when anything hit like trucks with tons of HP. Stupid power creep to the moon
•Syngonium help too for a counter team with her great def buffs.
•Spider Lily is great. Disgusting 60%crit dmg (second highest crit dmg for 5 behind Bluet if I'm correct) and usable debuff. She really lacks atk buff though.
•Pinkladies (Princess of Pure Flower) Good but the weakest Pinkladies version I guess. Flower Saint is way better.
•Dragon Tree is high risk high reward. I don't think she is that great but Combo Hit is a thing and may get a lot of kill if you gives her enough power.
•Statice. Never played her but I know some people liked her as support.
•Manchineel is an intercept girl and one of the few 5* with actual evasion post rework. No reason to not use her in your evade team before getting more actual 6*.
•Blushing Bride (Costumed Apprentice Teacher) is a decent support with Crit+Negate damages
•And Artichoke can be a good attacker.

I didn't checked all the girls. Only the ones I know they are or were at least decent. I could have missed some things. All of thoses won't change your team to make it awesomly strong. That's the job of pure 6* and only a handful of promoted 5* have insane potential. But decent promoted 5* is better than just nothing.
Having 12 rainbows at your point is not bad at all. I got my first rainbow after almost 6 months. The game was less hard and we didn't have any free 6* though. And a really unfair gacha (basically the salt ticket gacha but with FS).

At the end, you did not the 3oo FS new year gacha? Or did you forget about the free 6* ticket in the warehouse?


https://i.imgur.com/XD9m7AE.png
This is just a Ghost Weed skin. And it's a free one. You already have Ghost Weed (Princess of Pure Flower). You can use it on her (click the shoe icon on girls profile to change their skin). I think regular Ghost Weed is the weakest of them (useless out of Solar Teams and there is better Solar Girls anyway).