Mount&Blade: With Fire & Sword/Party

In the beginning you can fight looters and Bandits without a party.

Looters
If your fighting looters you can run away from them stop wait fire a good close shot with your firearm and repeat the process until you run out of bullets.Then pull out your melee weapon and pick off men that have strayed from the main body of the group until eventually you kill them all.

Bandits
Bandits have firearms so don't attack straight away instead circle them from a good distance away until they waste all their bullets(musket balls). Then attack with with your firearm picking them off with the same process as the looters, when you run out bullets attack with your melee weapon picking off men that have strayed from the main body of the group until you eventually kill them.

Buying troops
You can visit taverns at cities to recruit men into your party. This is usually a disadvantage from buying troops from mercenary camps. All nations have they're own mercenary camps, each camp has different types of mercenaries. You can find a mercenary camp by looking on the map. When you buy mercenaries from a mercenary camp you can change their weapons and armor.