With strength-9 indies (all I ever play), I can usually take a province every two turns when I get started. I'll take a turn or two to beef up my starting army, and then I go a-conquering.
After I've conquered the ring of provinces around my home fortress, then I can usually put a second army in the field and speed up to one (or more) provinces per turn.
I probably wouldn't be competitive in multiplayer, but I'm more-than-fast enough for SP. Sometimes, the AI will get a little ahead of me in the early game, but I always overtake it once I can get the war machine rollin'....
---
PS:
As others have written, the key to fast early expansion is Mercenaries. Hire up any mercs that are worthwhile, and use them to snag provinces while you build up a solid army of national troops.
Remember that your mercs are generally
disposable, so use them appropriately. Put the Brave Breakers, the Black Fists, and Dante's Stingers on the front lines and let them do the hard fighting for you. You're paying them to die for you! Meanwhile, you're recruiting a strong force of whatever your best national troops happen to be. Once the mercs are dead, you'll have a company of
Helhirdlings (or whatever national troops are best for you) ready to go forth and spread the word of your Pretender.
