Your first decision in Mount and Blade 2 Bannerlord is to choose the character's culture - it provides additional bonuses, but also penalties that influence the game. You can't change your choices during the game, so make a conscious decision. This page has descriptions of all cultures, as well as hints on which culture in Bannerlord is the best.
First, you should check all the cultures in Mount and Blade 2 Bannerlord. The following table lists the cultures available in the game, as well as their impact on gameplay.
Bonuses: 5% more reputation from battles, 15% more income from mercenary service. A 10% production bonus for villages that are connected to castles.
Penalty: Recruiting lords into the army costs 20% more reputation.
Bonuses: The cost of recruiting and upgrading infantry units is 25% less. Armies lose 20% less cohesion each day.
Penalty: 20% greater penalty to the relationship resulting from the kingdom's decision.
Bonuses: 20% less pay for the garrison. You gain 25% more influence for being in the army.
Penalty: Farm increase is 20% smaller.
Bonuses: The cost of creating caravans is 30% less. A 10% smaller penalty to trade. No penalty to movement speed in the desert.
Penalty: The daily wage of units in the party is increased by 5%.
Bonuses: The cost of recruiting and upgrading mounted units is reduced by 10%. 25% bonus for breeding horses, mules, cows and sheep in villages ruled by Khuzait rulers.
Penalty: 20% less income from taxes in towns.
Bonuses: 50% less penalty to movement speed and 15% bonus to range of sight in forests. Cities ruled by Battanian rulers receive +1 to volunteer growth.
Penalty: 10% more time to finish building town projects in districts.
The answer to that question isn't easy. The choice of culture in Bannerlord should be made based on your play style, but if you are a beginner we recommend the Sturgian culture. Their primary bonus is the reduced cost of recruiting and upgrading infantry units. Having no experience with the game, infantry should be the backbone of your army.
It is the easiest type of units to manage. Unlike ranged units, you don't have to think about proper positioning during a battle - you can simply send infantry to charge at the enemy. Also, compared to cavalry, infantry is cheaper to maintain and upgrade - training cavalry units requires horses at the appropriate level in your inventory.