9 concurrent wars. Not bad.
(The Mughal merchants collecting in Genoa and Lübeck 150 years into the game is also nice.)
For the lone tribe, your options are, from fastest to slowest (in game time), to:
- Vassalize/annex it (~15 years)
- Colonize until you get a border, and then conquer it (~20-50 years from the looks of it, depending on whether it moves by the time you're done coring the nearby tribe)
You can also:
- Wait for it to come to you, which it'll eventually do
- Conquer it directly, after unlocking the unrestricted coring range thing in the age of revolutions