[thejeff]

Luck works the same in SP and MP. It's usually considered one of the weaker scales. As your realm gets bigger, later in the game, the number of events (good or bad) is capped, so the advantages of luck doesn't scale with number of provinces the way order and growth can. Most MP players prefer Order 3 and Misfortune 1 or 2. It's a trade off.

5 or 6 dominion is about the minimum I'd use in MP. You can get away with less in SP. 9 or 10 for Awe, or if you're really trying to spread your dominion for some reason. A temperature dependent race (like Neifelheim or Abyssia), nasty dominion effects (like LA Ermor or R'yleh) Immortals?
You want to be fighting in your own dominion as much as you can, especially if you're using your pretender.

The important thing with a pretender is to figure out what you want from him. Rainbows can be useful for getting lots of site searching early on and later for forging and casting rituals. Most would only do this in MP if you have some form of very strong troops to expand with and hold off an initial rush. Elephants would be a good example.

You can also use a pretender for early expansion. If you haven't yet, try an awake Wyrm with no magic, good scales and dominion 9 or 10 for Awe. He should be able to take independents by himself from turn 2. Avoid attacking Knight provinces in low dominion. If he dies, call him back. He's got no magic to lose.
A Prince of Darkness with a few more levels of death can do the same thing, but is a little more fragile until he gets some equipment. Even cheap trinkets make a big difference. Since he has full slots, he can be equipped to stay a threat throughout the game.

I'll often try to design a pretender who can do a little of both. Expand my nation's magic diversity and be able to serve as an SC in the middle game. That depends a lot on what your nation has.

The other main use is to set up a pretender to cast particular late game spells. Wish, Master Enslave, that kind of thing.