Where you place your first Army card (after your starting card) dictates the possibilities you will have during your early turns. You do not start with a red Commander die at the beginning of the game, so putting the first Army card above or below your starting card will allow you to draw Command cards during your first turn (see the “Consult” action, p. 9).
If you have a bad roll on a Commander die, remember that you can use the Empower action to improve it. You may use this action multiple times on your turn if you want to.
Going for big or massive legions will give you several advantages. First, you get a bonus from the Battle Reward card. Second, you might cause an opponent to lose a Legion die after a failed morale check. Third, you get more Legion dice. The downside to this strategy is that you fall behind in the race to finish all 5 legion colors.
The Muster and Requisition actions allow you to manipulate the number of cards left in the deck of Army cards. This can change when the end of the game is triggered.
The Requisition action can prolong the game, or can potentially give you the advantage of triggering the last turn.