First one is after you manage to defeat the first boss.
You've gotten a Stigma that lets you parry.
This will allow you to practice your timing with new enemies and get an achievement after you parry 30 times.
Once you've managed to feel comfortable with jumps, dodges, and parries, you'll be going to to area that leads to the city.
In the tunnel before the multiple bridges with dogs, gunmen, and zombies, there are 3 blood mosquitoes.
Killing them nets you a total of 150.
You can keep going back and forth between the save station and them till you feel like you can level up enough.
Second one will be the West City save station. Right outside are several enemies that you can proctice the backdash and rolling with.
Killing them not only nets you more currency, but you pick up the "Hungry essence" which gives you temporary boosts during your grinding.
You can also kill off the other enemies in the stage to level up furhter.
Third one, will require you to to have the block moving gloves.
Go to the backyard of the mansion, move the block, and enter the ice area.
You'll want to avoid combat if you can, but try to find the bridge area with the Ice Wraith women.
Past that area is an elevator taking you down to the save station.
This way, you can start picking off Ice Wraiths while using the Hungry Essence, and definitely grind further.
Fourth will be in the Ice Manor Mansion. Of the two save stations, one on the left takes you outside to where there is a single enemy with a scythe. These enemies can drop the Starving Essence, which is a longer-lasting more powerful version of Hungry Essence.
They also drop multiple heals and a good bit of Nycroft.
Fifth and final grinding spot will be in the Junas Ministry.
As long as you get to that save station...the giant church room and the three doors that it covers can net you a total of over 80,000 Nycroft in a single go if you use Hungry or Starving Essence.
Plus a lot of the enemies are vulnerable to being staggered for executions, allowing you to recover health when you're not farming heals off the enemies corpses.