For windows you dont need to buy it, you can activate it using microsofts own tools, its on github (dont remember its name right now.)

As for linux, i would recommend openSUSE Tumbleweed, it is fresh, and the best part about it is that whenever you update the system, it creates a snapshot, so if the update had some kind of undesired sideeffects, you can just startup the old version. (These snapshots only effect the system’s packages, your apps will keep their state iirc. My brother uses tumbleweed and he is very content with it.)