In case you weren’t a die hard minecraft player, diamonds universally appear on y level 12 and below. But Hexxit Updated explicitly mentions diamonds are going to more plentiful so you spend more time whacking mobs then mining. My first two stone pick-axes brought me in enough iron for a complete set of armor, a sword and a pick-axe. On my next venture I’ve come across three diamonds already and might just stay down there until I’m encased in diamonds.
And then I fell asleep at 6 p.m.
Tonight is MC Eternal. It has just some amazing challenges and really looks like it designed for thousand hour worlds+. The questlines give gold rewards and there is a really well stocked store. In comparison, RAD (Random Adventures Dungeons) has a more moderate store, but also gives out gold for rewards. All the Mods 6 has no quests or rewards, as does Hexxit Updated. Enigmatica 6 has rewards, usually material components and bonus resources as rewards. TNP Limitless 3 gave out loot bags that had random rewards and that felt entirely too OP. There was another modpack Extravaganza, that gave out loot crates as rewards. Haven’t delved into Greedycraft at all but it looks like XP based rewards for the quests.