The best way to gain strength is to recruit tier 4+ clans and give them fiefs. Strength is parties + garrisons, both of which require clans to have money coming in. Passing polices to boost settlement loyalty and party size will be good. I aim for my kingdom to have 3 full rows of clans in the diplomacy tab, which usually equates to around 25k
The base size of your party in Warband, unmodded, is 30. This is increased by 5 for every point into leadership, up to 50 troops. Every level of charisma also contributes to one additional troop. For every 25 renown, your troop size is increased by one. Huller_BRTD Prophesy of Pendor • 9 yr. ago.
Bandit scaling, or basically increasing the size of bandit parties as you increase in level, is probably my biggest complaint about Warband. Fighting bandits as a low-level adventurer is fun and all but once you're ruling your kingdom or once you become a powerful lord, the armies of other vassals and kings should be your concern and not some dumbasses with oversized mallets hiding in a mountain.
VJiM.