Some easy strategy that worked for almost everyone (some first heroines just did somehow before figuring this strategy, and a gal with whole map AOE I poisoned with mass debuffers)
Place archers around heroine randomly so they are not killed fast.
Upgrade range for them and some damage, at some point start investing into quantity up around 60, then finish all archer upgrades and then finish all quantity upgrades.
Sometimes it is effective to place tanks on the line of damage, but usually archers are sufficient.
How it works: you gain exp for receiving and dealing damage to heroines (not damage probably placing attacks on them). And when heroine's HP bar is yellow she gets slowed down a bit, then on red again. You need to take her HP to 0 as fast as possible and then you just attack her and wait until she kills everything. This way you can gain thousands of exp per try, sometimes even 10k+ possible.
So earlier your archers can do damage to heroine, earlier they can take her HP to 0, the more of them you use per run -> the more exp you get per run.
Place archers around heroine randomly so they are not killed fast.
Upgrade range for them and some damage, at some point start investing into quantity up around 60, then finish all archer upgrades and then finish all quantity upgrades.
Sometimes it is effective to place tanks on the line of damage, but usually archers are sufficient.
How it works: you gain exp for receiving and dealing damage to heroines (not damage probably placing attacks on them). And when heroine's HP bar is yellow she gets slowed down a bit, then on red again. You need to take her HP to 0 as fast as possible and then you just attack her and wait until she kills everything. This way you can gain thousands of exp per try, sometimes even 10k+ possible.
So earlier your archers can do damage to heroine, earlier they can take her HP to 0, the more of them you use per run -> the more exp you get per run.