1. You may recruit as many troop as can however need watch out on the upkeep, never have higher upkeep than food income , the best is stay 10-15 % below the basic food income.
2. Try max lv the upkeep reduce in order to allow you have more troop and not go over the basic food income.
3. Before recruit any type of troop click the 'i' icon to check the stat .
4. Study the stat of the troop type to get the best use out of it for what you need.