maotd ; Cosmos I mention is Cat-ear hair style Cosmos.
I more familiar with Japanese name so sorry to make you confuss. oTL

ShadwNinjaX ; I agree with Myrdin this deal not worth.
In term of gold girl you can use event girl and do perma-event to get extra.
In term of gems we get gems easy you can collect 50 in month or shorter.

My opinion if you have money to spare and already willing to pay it's nice to pay for them to show your support.
In the end who will know maybe you can get 3 rainbow out of this deal.
You just got Anenone for me that's a good sign.

About rainbow girl deal I can say DMM don't sell them often as Nutaku do.
I can't specific how often they do since my native community give a lot of variety intel to me.
Some said 2-3 time per year, and some said it's at least 6 per years.
For more intel loitering around Himeuta might help. Good luck.