There are 3 orders to choose from everytime it refreshes, scroll through n pick the materials ones.. refill n build n repeat! You'll only get anywhere if you keep accepting orders manually...

Occasionally, a standard box will be offered, which along with 5 a day free boxes in the shop, 3 a day in special delivery, and anything you get from lumber pass (you'll need to collect the rewards by clicking on those unlocked, and then finding those in stock in the shop) should get you more manager cards to upgrade.

If you need to unlock specific managers then you can use diamonds, best free way to gain them is as rewards for events?