I'd do a factory reset
only in case the console hasn't been hacked before just so that you can start fresh and I'd just follow through the
Wii U Hacks Guide pages on how to setup Tiramisu.
Other than that, I'd suggest you check
NUSSpli (for downloading software straight from Nintendo Update Servers) and
Ticket Cleaner (for removing unused tickets for software that's no longer on your console), possibly
RetroArch as well (if you're into retro games).
EDIT: Few more things:
1) If you'd like to play Wii U, Wii and GameCube games, for starters, you can go two ways:
- 1 HDD for both Wii U games and Wii/GameCube games (that are played as Virtual Console injects).
- 2 HDDs, one for Wii U games and 1 for Wii/GameCube games (that can be run via USB Loader GX / Wii Flow on vWii side).
You should opet for an external HDD with Y USB cable instead of using something like a flash drive as those are more prone to failure. Something around 500 GB should get you up and running.
At the moment, I personally use one Y USB cable and two HDDs within two HDD enclosures, one for Wii U games on the Wii U side and one for the Wii/GameCube games on the vWii side. I just swap the HDDs to the one I want before I turn on the console.
There are setups for two (and three!) HDDs to work at the same time, though I haven't tested them thoroughly yet. I can link you the threads, if needed.
Important: Once your console format your Wii U HDD to its proprietary format,
NEVER AGAIN connect it to your PC as you won't be able to access games on it anymore. Wii/GameCube games HDD is fine to be connected as it should be in FAT32 file system.
2) If you'd like tu run RetroArch as well, I'd suggest getting a 128 GB microSD card, that should give you plenty of space. If you'd like to play only e.g. GBA games, you can save up some space on your microSD card by removing unnecessary cores.