Powering Up On the Cheap
Everyone wants to pump up their power, but how can you do it without dropping a fortune in Gems? Mounts and wings are expensive!
The best thing to do is to look at your gear and your mercs' artifacts. If you upgrade all your gear to +4, you'll get a bonus. If you can, try using Gems to quickly upgrade your mercs' artifacts. If you can upgrade your artifacts to a certain level, you'll unlock slots for glyphs, which add bonus stats. This way, if your character is weak, they'll have a full team to fall back on. Remember that no matter how much you invest in a merc, you can always transfer this investment to a more powerful merc when you acquire one.
If you're not getting a 5-star rating when playing Chaos Chess, you're doing something incredibly wrong. The reward chests you get for 5 stars are filled with Gear Geodes, which are crucial to having sweet gear. Upgrading gear increases all of your stats, including Charisma. Charisma directly boosts the stats of your mercenaries. Gear upgrades are the only way to increase Charisma.
Get merit in Merc Trials. Once you unlock the final trial in each section, spend all of your Energy in that trial because the rewards will be the highest. You'll have the chance to win upgrade materials for your gear, mount and wings in addition to EXP, Merit, and Potential.
When you first unlock Chaos Chess, don't be afraid to spend some Energy there to refresh and make sure you've won all the epic gear the system has to offer. After you've gotten all the gear, spend the rest of your Energy in Merc Trials. That Merit is precious!