Raven, when you look at Rich's list, be aware that the monster listed with each faction is "friendly" to that faction. So if you're in TB, you want to kill ogre lords, wisps, and demons in Fel to get silver. If in SL, you kill ogre lords, wisps, and silver serpents. If in COM, you kill ogre lords, demons, and silver serpents. And if in Minax, you kill demons, wisps, and silver serpents.
You also get silver by removing enemy faction traps or from an enemy being injured or killed by a faction trap you placed.
You can also earn silver by killing the infected NPCs and invasion forces in the towns in invaded towns in Trammel. You don't get silver from killing the crimson dragon, though.
Be aware that if the commanding lord has set the tithing rate to anything over 0%, some or all of the silver you earn goes to the faction treasury.