There is no best choice. Some pretenders are more effective at certain jobs. Machaka has lots of magical power, cheap archers and good melee units. If you want to use armies, you need resources, and to get them you need Productivity. To get your sacred Black Hunters or your best mages, you also need lots of money -> Order. Because Order lowers the chance of special events happening, you can usually take 1 or 2 points of Misfortune without anything too bad happening. Machaka also gets more points because they prefer warm lands (Heat 2), but they must take strong dominion so that their lands stay warm and they won't lose money. Because you are already taking high dominion (which is needed to recruit more sacred units) and you have good sacred units, you can easily take a pretender with high magic power which makes your sacred units better.
An example:
Lord of the Desert Sun:
starts with Fire 2 and Nature 1, Dominion 3
Take Fire 6, Nature 4. This gives your sacred units +3 attack and ability to go berserk. With this ability, after they are hit, Black Hunters get +1 to attack, strength and protection, -1 to defence and WON'T RUN AWAY. Very useful, but your priests are also affected. Try to keep them away from enemy arrows.
Take Heat 2, Dominion 6, as at least these are needed for Machaka. Then take Castle (80 points). You should have 205 points left. We'll take Order 3, Production 2 and Misfortune 1. You have enough points for 1 more scale. Because you have nature mages, you could take Death (scale) and get Magic(another scale). Magic scale helps all your mages research faster. As it is a small bonus to all mages, lots of cheap mages get more out of it than few expensive. You have cheap mages, although the cheapest, Witch Doctors, aren't good researchers.
You have good Fire and Nature magic, so now you've got Magic. Dominion and Scales are ok, although others would probably advise you to take less production and more Magic. Strength is also quite good: you have your normal national units (archers protected by hoplites), Black Hunters with very good attack and berserk, and your Pretender. Research Evocation 1 and make him cast Fire Darts. It gets more powerful with more Fire magic, and your Lord of the Desert Sun has plenty. Take him with your army, and his flames will be of great help. Then research Alteration 1 and add Eagle Eyes as his first spell.
You could also take different approach. As an example, Fire 9 would give the sacred spiders attack +4 and
flaming weapons... Or take Phoenix and high dominion. If Phoenix dies in positive dominion, he won't die but is reborn on your home province, and with good Fire or Air magic he can kill dozens of units before being sent back to capital to recover, every turn until he gets Feeble Minded or something. Then it takes few turns to go offensive again, as Immortal units recover from such wounds. Or you could take Oracle, get Astral 4-6, very good scales and fortress, and win with your national mages and armies. Your Oracle would give you access to different magic, and be able to forge powerful items like Ring of Sorcery or Ring of Wizardry that would help your normal mages.
re:ranks
It must be post count. They don't matter much: I have 1000+ posts, Zen 430, but he has done lots more to the community. There is 27-page-thread about his mods!