Thank you everyone for the replies. It's a nice surprise to see so many helpful replies appeared.

(consider how quiet the forum was.)
Now I am on the second island and won exactly 30 fights without loss. Here are the details of the army.
Royal Snakes 32/32 (I brought some reserves when I left Debir.)
Inquisitors 19/19
Royal Thorns 3/5 (I almost missed it.)
Archmages 5/10
Marauders 44/65
Archmages are very useful to me so I have to kick priests out of the team. (hard decision consider that Amelie is a warrior and haven't learned order magic yet, so no heal spell) Well, it's not as hard as I thought, at least I don't need to use heal scrolls. And marauders are pretty active as a secondary melee unit with a high initiative 6 and swiftly strike.The bonus from marauders is about 700*15battles = 8500 extra golds. I have bought a snake boots 6000 golds, officer's baton 8000 gold, pirate's halberd 20,000 golds(+3 attacks, 5% extra gold after battle)
Now I am ready for Bolo with 2056 leaderships and a scroll Call Colossus. So what do you think is the best 5 unit? I want to keep marauders as long as possible

Right now I am thinking about getting a red dragon. Amelie's mana pool is only 12

and I can't imagine how to take full advantage of black dragon. Or there are better choices?
p.s. kcwong, I assume you were talking about CIV IV, not CIV V, right? I just checked the official site again and the release date is this fall.