Must have foci

So I'm almost at the magical 70 and I have a couple questions. Last night I replaced my belt with Druzzil's Distance for one with Spell Haste V and I'm not sure I made the right choice. My old belt is in a bag in my magelo if you care to see. This leads me to ask:
1. What focus effects are must haves, what ones are desirable, and what ones aren't worth even bothering with?
2. Are DoN crystals my best bet in getting these? I am in a very small guild who are basically just a bunch of friends, I play very odd hours becasue of my job, and have only about 50K to spend on upgrades.
3. I'm thinking about replacing my weaker wrist slot with the Dawn Forged once I ding. Any suggestions for my next piece?
4. How far in to level 70 should I go as a safety buffer before I change to 100% AA exp?
Thank you guys
1. What focus effects are must haves, what ones are desirable, and what ones aren't worth even bothering with?
2. Are DoN crystals my best bet in getting these? I am in a very small guild who are basically just a bunch of friends, I play very odd hours becasue of my job, and have only about 50K to spend on upgrades.
3. I'm thinking about replacing my weaker wrist slot with the Dawn Forged once I ding. Any suggestions for my next piece?
4. How far in to level 70 should I go as a safety buffer before I change to 100% AA exp?
Thank you guys