One way of getting tons of experience very fast is to hunt sea raiders.
1. Get eight companions, which is the maximum I have been able to assemble
without them getting at each other throats, and go hunting sea raiders and
forest bandits.
My usual group is two melee beasts (Alayan and Firentis), two horse archers
(Deshavi and Baheshtur) and two specialists (Jermus the field surgeon and
Klethi the scout) Depending of what character I play, Ymira can be the
military tactician/trainer/engineer, and Bunduk the charismatic trader.
2. Give them all either lances lances, or ranged weapons. The armour will
come on its own, as you kill and strip the sea raiders, but weapons you'll
have to buy to get started.
3. Line up your companions on top of the longest, smoothest, gentlest slope
you can find. Make sure they are all facing forward. I do this by having them
hold a position behind the final one, and them asking them to advance. Be quick
about it, the sea raiders will be approaching fast.
4. Charge the sea raiders, lancing those who stray from the group. Try to get
them to chase you. This way, they will spread out, and some will continue towards
your companions. Deshavi, Baheshtur and whoever else has a ranged weapon
will do some damage. Once the sea raiders are at the right distance, order a
charge.
Start slow, with sea raider groups that you outnumber. As your equipment gets
better, and the groups grow, you will be getting a lot of experience, and so will
your companions.
Usually, by day 60, my character is level 25+ and my companions level 15+.
At this point, the nine of us easily take 40+ groups of raiders. It's not always
smooth sailing, but if your companions get knocked out, make sure you have
a masterwork light crossbow and some bolts in your baggage train. When
things look dire, ride back to the chest, get the crossbow, and kill the remaining
sea raiders by shooting them in the legs. Slow and boring, but safe as anything.
Doing this you get tons of renown and kings will be asking you to join
all the time. By that time, I usually have 3 characters with training 7+, and I
join the faction that appears to have the most clue, i.e. that is fighting ONE war,
against a close neighbor (as opposed to, for example, the Rhodocks fighting
the Vaegirs) If no king is this smart, take a 'peacemaker' quest from the city
of someone who is fighting TWO wars, and end one.
Chances are, you will be elected marshal in the first election after you join,
because your renown is out of this world. Time to show these pampered
nobles how campaigns are conducted... and one last hint. At joining, you get
a village. Every time you take a castle, ask for it, until you get one. Use it
to quarter the troops you're not using (i.e. your cavalry when you are taking
castles, your dismounted troops when you are looting enemies for cash, etc...)
Then do not ask for any more castles, until everyone in the faction has at
least one. Then, and only then, start taking cities, and never fail to ask for it.
Life is so much easier when you have rich cities to pay for your men.
Or you can start your own kingdom. Some people find it more satisfying,
but I think it is too lonely fighting the world on your own. It's more fun to
have lords and ladies to lead, reward and impress.