kjenks said:
Consider the Leadership feat to get yourself a good mount. A heavy warhorse is okay at level 6, but by level 12 it will die in the first couple of rounds of combat about half the time.
He's starting at 4th level so Leadership is out (for now) - requisite 6th level character.
I'd stick with 4 levels of fighter and none of barbarian. Reason being the increased movement of the barbarian doesn't do you any good when mounted and the extra feats you can get as a fighter more than make up for it if you want to focus on mounted combat.
Plus 4th level fighter can get weapon specialization (requires 4 levels of fighter class).
A fourth level human fighter gets 6 feats (if I've counted correctly, 1st level - 1, plus 1 (human), plus 1 (fighter), 2nd level - 1 (fighter), 3rd level feat, 4th level (fighter))
You can do a lot of tweaking with that number.
With 6 feats you can pretty much cover both the mounted archery and melee combat styles.
Mounted combat, mounted archery, ride by attack, weapon focus, weapon specialization, power attack. Although point blank shot and far shot are both viable options (drop power attack for point blank shot and pick up far shot later. At 6th level you'd get 2 feats if you went up straight as a fighter.
Battleaxe is pretty good weapon (x3 critical) - nothing says it can't be used when mounted with a shield