Sure. I've 100% completed WoL, and I'm working on WoD right now.
The biggest thing I can say is this:
If the enemy is 9K or higher, and you're not, don't worry about it. Come back later.
A big one people have trouble with is Zero Suit Samus/The Boss. This is designed for you to take her on when you have immunity to poison, and a spirit that is around or above her level.
I took her down when I had 12k power.
There are other fights that require specific customization.
Anyone going through this will eventually run into Paultine. This can be cheesed at any level.
To do that, do the following:
Use the spirit that gives you the staff weapon, and equip two ammo boosters.
Get on the platform furthest from Daisy, and nuke her. You can end the fight in 3 shots.
Outside of that, I think it's a case of ask and answer for tips, really.
I was just curious what everyone's max is. I was stuck at 13k for a long time, but jumped to 17k, and plan to see what the highest level is. I'll know before the weekend.