One thing you may not know about free energy is how to make full use of it. How to pool it beyond the normal limit of 5 in arena, or 4 in raid bosses. Doing this, it's possible to get 12 wins in arena using nothing but free energy alone.

The trick is knowing when the game uses energy and when it does stuff. So to walk through the steps to taking advantage of arena energy, the first step is go to the arena, then choose someone to fight. You'll then be at the screen where you see a shadow of the other person and what guild they're in. Confirm you want to fight them. Now you're at the screen where you see all 6 knights and there's a button to start the fight. At this point, you've committed. Your energy has been spent and you've started regenerating your lost energy. But you haven't started the fight. If you wait 25 minutes, you'll be back up to 5 energy but still in this fight, essentially increasing your max free energy pool to 6, instead of 5. This opens up a few options. You can either go straight to the 6 win streak bonus and get your two extra energy to do with what you want, you can get the 9 win streak bonus in only 25 minutes time, or you can go for the 12 win streak bonus if you're very patient. Going for 12 requires doing this twice. Once to fill up to 6 energy to start with, and then immediately again for 9 minutes. You need to do it twice because once you finish the first fight, you'll be back at 5 energy and not regenerating anything, so you need to start regenerating free energy but also keep the streak going.

The usefulness with raid bosses is a little more limited, but still not something you may know about. If you follow the same steps and get the fight with the raid boss ready without starting the fight, you'll start regenerating energy. This is useful if your schedule is a little busier. It's also useful if your guild does level 3s and likes to leave bosses with 20k health. If you start the fight against a boss with full health (or at least enough health for you to not kill it), you don't have to worry about it being dead or left at low health when you come back. Once the fight is prepped, that's what the boss has for you this fight. You have until the boss would escape to finish the fight. You're technically doing 100% overkill to the boss if you come back to finish the fight when it's already been killed, so it doesn't really help the guild rankings that much but it's still something.

Unfortunately, this doesn't always work if you go to other apps. I notice that if I come back after too long, or if I've been using too many other apps, that KnD will have to restart when I try to come back which does set you back, so it's inadvisable to leave your fight prepped for too long.