watch dogs 2 is absolutely worth it. its honestly the only good one in the series imo. and u dont have to have played the first one to understand what happens in 2. there's a few references to the first one, the mc aiden shows up in a side quest as a little easter egg and an important npc later on is from the first game but the other characters basically explain what u need to know about him to each other. one of the dlcs also has a character from the first game but at most any reference to 1 is "OOH ITS HIM!!!!"
otherwise its better written than 1, or legion, the characters are more loveable and memorable, has way better quests. and just more fun in general than the other two games.