In 2nd haft players have bigger bonus so dont use radars or glasses in first half of this event.
Use 2-3 e-gache + 2-3 card revial when 2nd half of event starts and hope to ger 1-2 R slayer girls - each e-gacha have ruound 50% chance of giving a R-Slayers girl.
Get both N slayer girls forn N-Gacha. Get all slayer girl to level 100 or higher.

Get 50.000+ Points at all the past 8 times thay had this event. Newer spend a single $ on this game eigther.
At end of this event I will have more glasses and radars than at start with. Prity easy event for f2p - if you are smart.
High level help too in this event.