There are four clans to choose from in Shogun Wars. Depending on your playing style, any one of them may work best for you.
If you intend to play with a heavy offense, play Mantis. They get a large increase in attack power. (+65% Strike Action).
If you intend to play a heavy defense, play a Tiger. They get a large increase in Defensive power. (+80% Defense).
If you value knowledge of your opponents, or want the ability to hide your own resources, play a Scorpion. They get a bonus to Ninja and Shinobi scores. (+32% Covert).
If you really don't know, or think it is likely that you will play several strategies over time, play Crane. They get a smaller bonus than the others, but the bonus is applied to gold. Therefore it allows the most flexibility in tactics. (+20% Gold).
. They get a large increase in attack power. (+65% Strike Action).
. They get a large increase in Defensive power. (+80% Defense).
. They get a bonus to Ninja and Shinobi scores. (+32% Covert).
. They get a smaller bonus than the others, but the bonus is applied to gold. Therefore it allows the most flexibility in tactics. (+20% Gold).