Best way to project, plan and structure an app with CI

Very good thread!

I‘m not sure how to start the best way. As many people would say ... it depends ;-)
But I would say ... first I create the header file to implement bootstrap, jquery and custom webfonts.
Then I create the most important and nessecary model(s) and controller(s) < first model, then controller to load a first view and provide data to it. Mostly the view just displays a list of loaded items.
Then I build another view to show details of one item. Often this is a form so that I could build some edit functionallity extending to CRUD (create, read, update, delete).
After that i want to make it look nice. So I tweak the css (scss). Now ... display-filters for the list. So some jQuery scripting :-)
If there should be users I would build the login now, also with session-management. Just the login, not the whole registration and forgot-password-stuff.

Before the software grows, I also try to build repeating view-parts to be flexible.