There's a 60 aurora daily using paid aurora.
I use it cos then it comes down to £0.86 per draw which is still pretty bad but no where near as bad as £4 per draw
It's the only feasible way of maximising my chances of getting event cards without using up too much of the limited aurora
The guaranteed 5* paid aurora option isn't too bad either if I was really desperate for one of the event cards, but is still more expensive than a daily £0.86 draw overall
EDIT: Burned 25k aurora trying to get akane but got 3 shizurus T_T