When should I start reading the Dark Tower series?

Here’s what I’ve read:

Carrie, Salem’s Lot, Pet Semetary, Cujo, the Dead Zone, Desperation, Rose Madder, Dolores Claiborne, the Green Mile, Misery, the Shining, Doctor Sleep, IT, the Stand, the Long Walk, Different Seasons

Next on the shelf I was planning to read: the Bachman Books (Rage, Roadwork, the Running Man), and the Regulators. I have almost all of his books on hand, just seeking advice on what else I should read before I tackle the Dark Tower series.