I don't know, just by looking at the names I'm not sure. For character progression which one will be need the most and which the least even though I guess they're probably all needed at some period in the game.
To briefly answer some of your questions.
Army requires some prerequisites:
Gold to buy, train and equip soldiers. Generals to lead them. A place to keep them, a castle or fort and then it all has to be maintained.
Your Army runs on its own turn base to your personal Character so they will not be assisting you in personal adventures. I do have plans to create a familiar option that you can have with you and thus aide you in battle.
Clans / Kindred is necessary for you to establish a proper army as it is where you establish your symbol, rules, taxes and benefits. You will also have to recruit actual players who can then be your allies and thus not attack you.
Wizard: You can do either one to start but to advance considerably you will need a clan because no large Army can be formed if they do not have a banner or symbol for which they will fight.
Hunter: As you take on bigger things the gold coming in will also be plentiful, however there are still lots of places in ROK II that needs writers to fill in descriptions. These pay 50 gps! The Archives pay 15-35 gps. Someone consistently writing can rake in lots of gold in a short period but it of course takes some effort like anything else in life.