As said before, there are tons of ways to make money.
Read up on trading, there are plenty of posts on that in both the general forums and around here. Buying enterprises is a must (do so at as many cities as you can after making some scratch the other ways)
Taking prisoners with manhunters and companions using blunt weapons from horseback (using no infantry or archers so you stay fast on the map) and having a decent prisoner management skill (4-5 points) nets a lot of money quick, along with a lot of experience from bandit hunting in general. Added bonus of high resale loot from sea raiders in particular. (This is my personal pick for the best way to get fast cash)
Tournaments are a fast 3000 and give you a chance to hone your fighting skills.
In general I always suggest making a lot of money first and then training up a strong army later - 60 men is way too many for the "bank up" stage. If you only had 1000, you're about 50x lower than the amount you should have before getting into the fief/vassal type stages. You really only need 5-8 companions and 20 manhunters (trained as high as possible) to start building up your wallet.
Then, once you have some strong gear (52/16 armor, 33+ boots, 8+ gloves, 50+ helm, masterwork or balanced or heavy weapon, reinforced shield) and a hefty amount of money THEN you have some security for when you do start on the vassal/fief stage of the game.
Companions are one key to success, make sure they have decent levels of trainer and other party based skills (three skills per companion is a good start) and that they have decent gear loadouts. Riding 4 is a must, and any warhorse or charger type. Companions tend to do best with a strong shield and one-handed weapon that does not have a thrust (So Axes, hammers, morningstars).
I won't go into how to build a character for success as there are so many different ways to play it, most of which deal with taste rather than maximization. Needless to say Charisma builds are very effective with high leadership, moderate prisoner management.
Good luck and welcome to the floris mod
EDIT: The state of banks is incredibly ridiculous right now, and I avoid them altogether as they feel like cheating. But you can just invest whatever you make money-wise in a portside bank (Sargoth and Praven I think are the best) and just keep reinvesting whatever you make from enterprises and the interest. They become moneymaking machines that give limitless denars. So if you don't mind being exploity, you can do that and make the game very easy.