I'll start with the concept of Language Families. Read that article, it explains a lot.

Then look at the list of language families. You'll start to see that what you're asking is pretty complicated. I got this video from my library a while ago which is very good.

I would start from your "target" language groups and work back from that. I want to know Russian so I'll learn that which will help with other Slavic and East Slavic languages languages.

I've not searched but I'm sure there are YT vids about language families too.