You'll pick up event girls and with a possible anniversary event for 1 year on nutaku in the next few weeks I'd at least hold them till the end of the month

The 'hold till ticket' is the BEST bet but it is dull and boring, the right and sensible thing generally is

Never use your Flower Gems on the premium gacha. It's a trap. There is nothing more than the available girls before the current event in.
Use them on the priority gacha only if there is a featured girl you really want. If not, don't spend on it. Or you can try if you really need a new gold but it's not advised. But keep in mind that "increased chance of getting featured girl" means "slightly increased chance to get the featured 5*/6* ONLY if you get the 6% or 0.5% to get the 5* or 6*.
Keep your FG for the rare ticket gacha. It's the better and safer option.