You’ll unlikely need a preamp/DI as the Duet will have an instrument level input (read: DI). With that in mind, a Preamp will just give you EQ flavour, which is fine, but almost always achievable within the DAW you’re using, which allows more mixing freedom.
Based on your usage, I’d probably go with a fairly powerful laptop (I’d say a Mac Book with at least 16gb RAM). If you have the budget, get an additional screen for home use, that way you can work on a two screen setup at home, while also having a mobile setup via the laptop.
Boom, sorted.
At some point you’ll likely add an external hard drive for storage/backup, but you’re unlikely to need/want that immediately.
I’d also recommend Logic as your DAW if you go Mac, cheap for what you get, and nicely scaleable from beginner to professional.
Si