Best farming stages are
IW-8: RMA70-12
IW-7: Orirock Cluster
IW-6: Integrated Device
Farming efficiency: for the original run was Devices > RMA > Rocks
Credits to Daniel O’Brien on Gamepress
For new players: you can ignore furniture in event shop, you will get it year later for free when IW will be added to side story tab.
For veteran players: buy all furniture, Kroos alter pots and you must complete at minimum these stages: IW-1, IW-2, IW-3, IW-5, IW-6, IW-7, IW-8, IW-9, IW-EX-8 CM
Finally cleared the event shop, feels good.