Original Sin 1 or 2 First?

Do I need to play Divinity: Original Sin 1 to play 2? No, the stories are completely independent of each other. Divinity: Original Sin 2 is also very different in key battle mechanics--running a party style that works in the first game will struggle in the second game.

Should you play Original Sin 1 before 2?

No, there is no requirement to play Divinity: Original Sin to enjoy playing Divinity: Original Sin 2. If you have played Divinity: Original Sin however, you might just find a few subtle throwbacks.

Should I get divinity 1 or 2?

Part 1 is a much better game than part 2. Part 2 has a marginally better story, but its story is still not that great, and definitely nothing new/original/innovative that hasn't been done millions of times before. And Part 2 also has much worse pretty much every else (other than graphics).