I managed to make many nations my ally but I see Mydgard gone further. I don't remembver if I ever succeeded to make Pontus, Armenia or any country in the north (except Britanny) and the ones that I forgot.
So here are my observations about making allies:
Phoenician-ruled nations - except Cartahgo (Hispania, Sicily): diplomatic, agressive, o.a.
barbarians (Britanny, Dalmatia, Arabia, Mauretania and almost Scythia [they'll never join] ): agressive, o.a.
Greek-cultured nations (Macedonia, Thracia): diplomatic, diplomatic, o.a.
pirates/raiders (Cilicia, Cyrenacia): friendly, o.a.
Egypt (heh, only for the solidity
): friendly. friendly, o.a.
And there are Narbonensis and Mesopotamia. I think the first is diplomatic, agressive, o.a. the second might be a simple agressive, tho I wouldn't call the people of that land barbarians. I'm sure I managed to make both my allies, but now I don't remember with which attitude. I'm only sure that dipl/agr 's combo will be effective.
If you have any other nation's attitude I'd appreciate your tips.