Abhi my strategy will be slightly different from the early days, when I used to always get food and speed potions. Now that I have so much of both, I focus more on supplies for my best pillars, and precious gems. Because the Reward locations refresh so quickly, one can opt for two items at every tier if desired.
I'm running low on iron ore and tin as I constantly make iron bars and bronze bars for leveling up when I'm close by a couple million. These days levels are running at 19 million plus, so that's quite a few days of gameplay between level-ups.
Very little equipment is worth buying, other than the stuff that costs gems. But 5-6 gems per round is a bit low, in my view.
Ancient scrap metal and dragon ingots, amethysts, rubies, marble, shale and bamboo, and topaz are good. Will definitely get sapphires from new Greece Reward. Orichalcum, volcanic ore, adamantine steel and ore round out my selections.
Adamantine steel gives great pillar results: 2+ levels which results in close to 1.2 million energy. Solid progress gets made.
It's a fun week for the first 5 days; I always start to get a little tired of it near the end, lol. Find myself going back to my quest to move it along.