Twilight Forest is also resource rich, and its dungeons are pretty rewarding. Dying is a problem as in my experience had me respawn in two different locations, but setting the Minimap to automatically create Death Points helps to get back to where you were, hopefully without your stuff despawning.
Among the things you can find there is a type of magic map that can map out underground spaces for you and can be upgraded to show ore pockets as well. You can also create an Uncrafting Table, which allows you to repair things often more cheaply than the Anvil, recycle things, and even craft new tools and armor while transferring enchantments over from old tools and armor. With gold being renewable from Zombie Pigmen in the Nether and Kobolds in the Twilight Forest, you can enchant Gold tools and armor, possibly combine them on an Anvil to get the enchantments you want on one item faster, and then Recraft them into Diamond tools and armor. The Uncrafting Table's recipe is tricky to find in NEI as it's purposely a bit hidden. When you find a maze token or something called pretty similar, surround it in your crafting grid by eight crafting benches. It does cost you exp to repair and recraft enchanted gear, but the cost is linear according to the components you're replacing, if I remember correctly, compared to the Anvil raising exp costs seemingly exponentially.