From what Ive seen, the "plan" is to have you finish your capstone dungeon - then farm the world tree and "hope" to get a sigil for a nightmare dungeon. Repeat the process until you get a Nightmare dungeon that is tier 3+, then once thats finished you can finally craft and salvage sigils at the aspect merchant. Which should have given you enough powder to do them on repeat if you so wish, as they are the best exp/loot you can get. You can skip the world tree grind by just getting someone thats already done it to carry you in their Nightmare dungeon, just like capstone dungeons. (which you should be grouping anyways, as the exp for grouping is much higher.)
Helltide, World Bosses, and Legion events drop materials that you'll need to upgrade armor, weapons, jewelry, socket stuff, enchant stuff etc. As sacred (WT3), and ancestral (WT4) continue to raise the costs of doing these things with new mats required. World boss takes maybe 3 minutes to do on average, with no fear of losing. Legion events seem like a bit of a chore because everything blows up so quick, so you're effectively just running from one spot to the next. Both of these things will get better with time when the population dies off, but its disgusting to do right now. Helltide, I havent quite got the hang of it - I know you can get some nice stuff, but going in solo is some boring shit because... as noted above, the monster population is just too sparse. You go into a spot, blow it up and then you're back on your horse running around looking for shit again. Once you flip it to WT4, itll get better - but then youll have someone like Reefah come in and blow it up and the whole process will start all over again for that world tier.
