I usually recruit the following: Brawlers, Butchers, Farmhands, Caravan Hands, Apprentices, Tailors, Masons, Wildmen, Militia Men, Hunters, Lumberjacks, Witch Hunters, Raiders, Retired Soldiers, Deserters, Adventurous and Disowned Nobles, Swordmasters, Squires, Sellswords and Hedge Knights. Mercs from those backgrounds, even cheap ones, stand a good chance of having decent base stats, relevant talent distribution and good traits, and thus can potentially be developed in proper fighters, rather than fodder. Sellswords, Adventurous Nobles and Hedge Knights naturally stand out as the two most expensive and most reliable types of recruits. While it's not required, it's natural to strive towards eventually replace all your initial combatants with mercs from those backgrounds. You are unlikely to complete the process, and will likely settle somewhere in the middle. Swordmasters and Retired Soldiers might not impress with their stats, but i find it worthwhile to keep them anyway, for the excellent Events if for nothing else. Militiamen are a fairly reliable, if often expensive, pick, but frequently disappoint with bonkers stat distribution, so take caution. Hunters and Lumberjacks, i find, are the most reliable choice for their mid-ground price and maintenance. And, well, in a pinch, fodder can be hired from any background - daytallers, messengers, fishermen, what have you. And due to talents and traits, occasionally even a lowly Beggar can become a really good combatant.
