Once enchantment opens up, you will have a way to power up any piece of equipment that’s already equipped on one of your heroes, using any piece of equipment that’s not equipped on any hero. This will boost the statistics of equipment and is most effective on rarer, green or blue (or better) equipment. Once that equipment is merged into your hero using promotion, enchantment points will be converted back into enchantment dust that can be used for enchantments again.
Plus, the equipment that you use matters. When your heroes equip something, it’s bound to them until promotion time, and your promotion stat boosts vary depending on what equipment you have. So the more rare equipment, the stronger your heroes will end up. Of course considering you have near infinite levels of promotion, there is plenty of time to find ways to give it to your heroes.
In addition to the above, the equipment your troops can don will change depending on their promotion level. Rarer equipment (and more powerful equipment) fits heroes whose promotion levels are higher. You’ll know which equipment you can give up in enchantment by looking at its info to see who it fits, and also by checking the price for selling it or the color surrounding the icon.
Try to get a healer into your party by any means. A chaplain, for example, has a special skill to heal anyone in battle, and when this skill is upgraded past level 15 it can have a HUGE, permanent impact, which can really help sustain your party during tough battles or during the arena fights.
Pay attention to the popups whenever the player level is increased, so that you can see if the max hero level goes up too. When it does go up, immediately go and use all of your experience potions (not salves as those are too valuable) to level up your heroes – or, if they are very close to the new level, simply engage in one more battle for a quick level up.