There are 3 pink slayer cards you can get from the normal gatcha, 2 alpha, 1 beta.
Tossed you a friend request, I've usually got a few silver and gold chests waiting to be opened. (couple gold close to expiring currently)
As for the event, you do the event areas and you'll randomly find keys and cases. People on your friend list can use keys to open your cases, and you can use your keys to open their cases. The more friends you have the better. You'll need to periodically check your opened cases as well to accept the finder reward for opened ones. Lets see, other things to note... If you buy regular gatcha tickets with pero (9000 for 6) you'll get 6 pink keys as a bonus, you'll get a limited card if you get 50,000 bouquets, and limited cards when you clear stages 100 and 200 of the event (probably not gonna happen if you're new though, unless you spend a decent chunk of real money on peronamins to continually restore your stamina).