When there's not an event on, I like to keep 1,000 in reserve and buy mystery boxes with any donuts over the 1,000 to get my % up. We've had a lot of events and mini-events lately that have been very premium item heavy so my 1,000 soon drops down. I've been buying the premium items for this event as they've been hitting and I'm at 600 still. I farm every four hours so I should be ok to get all the items for this great event and then I'll get my reserve back up to 1,000 and plod along with the mystery boxes to increase my % multiplier.