OSRS Player Trying out Modern RS, some questions

Hey all I’ve spent the last couple days trying out RS3, trying out Ironman on this side of the puddle and have a few questions about the stuff I haven’t seen before:

  1. Is there a tutorial for divination of some kind? It looks like every single skill has some level of explanation on how to train it and what it’s for except for this one? I could check the wiki on how to do it, but I’m looking for an ingame explanation preferably to get my feet wet on the skill.

  2. I don’t really understand dungeoneering. Conceptually there’s something fun about it, I’ve hit 30 dungeoneering in a couple runs after finishing the tutorial complexities, but I don’t think I understand the point of it all. You get points to buy various rewards but what does leveling up the skill even do?

  3. How the hell do I acquire large quantities of pure essence? Is OSRS there are so many things that absolutely shit the stuff out that it’s not a challenge, but I’m wondering what options I have that aren’t just going to the mine as if it’s 2005 all over again.

  4. Is there a good way of figuring out what summoning familiars are worth making a supply of? Going down the list on the wiki seems a little overwhelming at first glance and if there’s a good way to find recommended ones for various uses it would be appreciated.

  5. I’m doing all the 5th age quests before tackling on the 6th age stuff. This is absolutely not optimal, but I like the narrative consistency of it. I see that necromancy is in the “age of chaos” period, assuming by the placement on the timeline that it’s a post-6a skill narratively? I’ve heard it’s a controversial skill, what am I missing out by not training it early?

If there’s any other tips you can offer I’d appreciate that as well. I’ve done the early game suite of quests that provide lots of combat xp: waterfall, fight arena, grand tree etc and now am looking for other quests that provide worthwhile rewards.