Oh, my. That's a can of worms. Aside from the Dark Tower books there is no real order. Though some other books have a connection to the DT books, it's not is such a way as to require they be read in any order. You will get many recommendations
The Bill Hodges Trilogy should be read in order. So should The DT books. And Shining before Dr. Sleep. then its kind of interesting to read the Castle Rock novels in order; Dead Zone, Cujo, Dark Half and Needful Things. Its not necessary though. You could do the same with the Derry novels starting with IT, Insomnia, Bag of Bones, Dreamcatcher. A fun thing but not necessary at all. But basically you can just skip around witthout missing anything vital.
Christine appears in IT, and seeing how you've already read IT I would recommend reading "Christine". The Shining also directly connects to IT as Dick Hollaran is mentioned during "The Black Spot" flashbacks.