Cooperation with the Dwarves of Erebor is vital to challenging them, understand expansion is going to be slow and be careful not to overextend yourself. Rhun is one of the strongest Evil factions in vanilla because of how they go unopposed in their expansion (this is rectified in Divide and Conquer sub-mod). Nab rebel territories in the East and South before focusing on Rhun. The Dwarfs of Erebor are right on your doorstep, be best buds with them through the rest of your campaign. This is useful for either Good or Evil but Good benefit from it especially. Send your diplomats to the far corners of Middle Earth, from the Variags of Khand to the Grey Havens and everywhere in between, get those trade agreements going. The forces of Good (unless you're Eriador) have quality over quantity, this means that good economies are vital to stemming the tide of Evil.
