Quote Originally Posted by Kotono View Post
It is very easy to reach stage 500+ on first playthrough, but you have to level your nymphs to level 10 for the super damage boost and level 10 skills.
Dragon and Snowfox are the two I focused on at first. Evolve both to stage 1 or 2 and they oneshot everything all the way up to stage 501, where the monster HP gets a x10 multiplier from the previous stage. Can still go on past there, they just need 2 hits now.

This is an idle game, so some patience is needed - or you can buy the gold boosters and things go wayyyyyyyyyyyy faster. The 7 day boost is well worth it, and it lasts through rebirthing. If you are absolutely determined to not spend anything, then the 1 hour boost is suggested on a fresh start/new rebirth.
Sure, I could reach level 500 on my first play through over the course of a few days. I say it's better to reset a few times over the course of those few days and come away with certainly more shards, almost certainly more bosses beaten and hence chances for good drops, and likely more hearts as a result of having more chances to have them drop.