Let's see, for writing I use Google Docs. While I'm in the "figuring things out" phase, I'll share the Google Doc with some friends and they can go in and makes notes and comments right in the document live, which is awesome.
For creating the artwork, I use a combination of Photoshop and Clip Studio. I do most of the work in Photoshop, but I'll do a lot of the backgrounds and the manga-style flashback inking in Clip. I use TinkerCAD, a free browser-based 3D modeling program, to make rough models of my backgrounds to draw from, so I don't have to math out all the perspective as I'm drawing. The program is aimed at children, so it's super easy to use. I'll also use Google Sketchup and the Sketchup Warehouse as a reference for 3D models of things like cars and Vespas and once for this fancy water fountain. It's just so much easier to have a 3D reference to draw from for complicated things like that.
Everything else, I do in Photoshop, though I am trying to transition to Clip Studio for future projects, to try and escape having to pay the Adobe subscription service for the rest of my life.