Region restrictions can be super complicated, definitely. Here are some ways to make things easier on yourself.

1) You can check Steamdb directly and look to see what packages are available. So, for example, Slay the Princess has been bundle a bunch of times but there is only 1 listed package and it has no known region locks so you can gift it anywhere. On the other hand, Blood of the Dawnwalker has a whole list of packages with different region restrictions, so you would have to see which one(s) activates in your region to figure out which key you have.

2) You can use userscripts to check regions for you automatically. There are two main ones that are very useful: Lext's Region Lock Checker and yannbz's Region Lock Helper. The first works on the SG giveaway creation page and will scan Steamdb for all packages purchasable in your country; it will then set the proper region restrictions for you. The second works on the store pages of certain retailers. So you can know how restricted a game key will be before purchasing it.

I hope that this helps!

Thanks :)