Whether using Windows or Linux, I have several pieces of go-to software I always seem to automatically install. I use Linux almost exclusively on my laptop, but I also have a small low-power media center PC that runs Windows 10.
These are also all free and mostly open source (although I use the paid version of LastPass for some extra functionality).
Mozilla Firefox browser - I like the speed of Chrome, but not the lack of privacy controls. Also love the "live bookmarks" feature.
Dropbox - backup and synchronize files on multiple computers.
Libre Office - don't need, can't afford Microsoft Office.
VLC media player - love this thing!
LMMS - Linux Multimedia Studio, for Windows too, despite the name.
GIMP image editor - I don't use all the features, and if I could reliably use Paint.NET on Linux, I probably would.
LastPass - online password manager