obsolete
Deity
So what was the big diplomacy situation like around 1000BC in you game? Was it like "oh no... I will give you my women so you don't attack and I can build my shinny wonders..."
Just kidding...
Actually, we start off with a penalty. Immortal levels give you -1 with everyone behind the scenes. This you have to over-come. It gets worse, because Brennus always starts with a -1 as well. So that's two for us to climb just to get neutral lol.
Good news is he doesn't just attack out of the gate, gives us time to prepare. While his peace weight is 0, that's actually not as bad as it looks. His pp is 20/70/100/100. So, even with a weight of zero, we can still lock him into being our blood-brother. Opening boarders helps (a little), but the main reason we did that was to get his religion in. This gives us up to max 3+ for same civic (OR) which is cool because this is one way to befriend Brennus early. And sharing same religion will give us double, which puts us at +6 max. And then we have the +4 for trading/gifting, not to mention resources, etc. And with all the random events now, we also kept getting +1 & +3 diplos by sending him our graneries, etc. So.... what I'm saying is, get him to Pleased mode and you're locked in friendship, there is no need for Friendly status. I think the misconception that Brennus is another Monte is due to the fact that he was new (in Warlords) and people weren't that used to so many aggressive style leaders.
It is ironic, but Bismark, who has a much higher base peaceweight, is infact much more risky, because his pp is something like x/x/90/100. So even when his weight is at 6, if you fail the logistics check with him, there is still a 10% chance he will declare war on you... EVERY TURN!
Note: Just don't open borders too early, or they will swarm you with landgrabs.