The order in which heroes are recruited does not effect on their base damage or health. Every new hero will have more of both stats. The largest difference is their abilities. It does not matter which one is selected first. When recruiting heroes, consider choosing those that you already have Gear for. Heroes will be very useful after leveling up. To get the option to level up, maximize their level upgrades. Keep things balanced and start by upgrading all your heroes a few times. Then level them up one at a time. Start with the first Hero you obtained, then work your way to the better and more expensive ones. You will probably get the maximum level upgrade for one herom and the cost of leveling up will become too high. When this happens, work on the better heroes. Do not ignore your heroes' health. High health allow them to survive longer in battle, lessening the time you need to wait for them to revive.