I almost never hire the mercenary raiders or ranged infantry because they use precious leather and furs, respectively. Diamonds, cider, and metal I can more-or-less reliably get, but when all but two of my workers are busy with upgrades and my village fills with bears, boars, and stags, no small game spawns to let me get fur and leather from hunting. (What fur and leather I do get from raiding or the daily dock bonus I hoard for blessings.) When my workers finish and are free for an animal blessing binge, I will hire mercenary foot soldiers to use up the sudden glut of fur and leather once I have as much as I can store. Then I settle in for another upgrade cycle where I can't get them at all.