Haha, patches are updates, usually bug fixes, but sometimes additional content, which are added to games after release.
If you've got vouchers / whatever, there's no reason not to buy it. You will still get the patches when they are released (like Skyrim).
You can choose to begin playing as is, or you could buy it, and then just wait for the patches before playing, like I have done with X4. (Bought it on release, (before actually) tested it, now leaving it until V3.0 and the Split Expansion releases.)
All depends on how eager you are to play it. Apart from anything else, I'll wait until it's at least 25% off, maybe even 50%.
By then it will be well patched and optimised etc.
(Have you watched the Witcher Netflix series btw? Was better than I expected actually.)
--A