Originally Posted by Unregistered

assuming everything in the gacha has equal chances of coming up... then an average of 2% of the players will have to pull everything on any individual box. with 8 boxes (7 resets), that means about 1 in 7 people (just under 15%) will have to empty the box at least once during the event. Of course the flip-side is that 1 in 7 will get the main prize on the first pull in at least one box also. All you can do is hope the higher the cost, the fewer pulls you'll need ...
someone calculated that it would take 63,000 coins to get everything, 36,750 on the last 3 boxes (4th skill, 4th equip, 5th skill).. so if your F2P, and you're running out of time, you might consider not using your skill blooms until you know you have 4 of them... and then buying a skill bloom (bronze? gold?) and using that FIRST,
(Caveat-I'm new, and have never bought a skill bloom with life crystals, so i'm a little unclear if a "bronze" skill bloom only works on a 2 star girl, or just as a second skill, or what the grades really stand for)

Skill bloom colors match the girls they're meant for. So gold skill blooms for gold 5* girls, silver skill bloom for silver 4* girls, bronze skill bloom for bronze 3* girls.

If you have any rainbow girls, or think there's a good chance you'll get one sometime (only guaranteed way would be through certain weekend gachas, but not this weekend), then the rainbow skill bloom should be what you're saving up for.

Second choice would obviously be the gold skill blooms for 5* girls. Don't waste those things on event girls. Even a F2P player will eventually pull a gold girl from gacha, and that is what you should use the gold skill bloom for. Except for Lavender, Edelweiss and Mountain Lily, event girls simply aren't as powerful as the gacha-girls. On top of that, you'll eventually see a revival of their event anyway, so you'll be able to upgrade them sometime anyway.

Silver skill blooms... Well, if you don't have many gold girls yet, and have the life crystals to spare (but get the gold blooms first anyway!), then you might consider getting them, though I'd rather invest in the ampies or lvl 100 manyus.

Bronze skill blooms: don't buy those things! At some point, which will come sooner than you might expect, you'll have your bronze girls replaced with gold/silver. Around that point, you'll also start to use the seed-gacha a lot less, having maxed out most of your 2* girls and well on your way to get all skill levels and equipment slots for the 3* bronze girls as well. A lot of players simply sold all their 2* and 3* girls at this point (I kept them, lol), and use the seed-gacha as a bank, to draw girls and sell them for 250 gold a piece. Which yields a lot of coin if you have a backlog of 150,000 seeds.