Below I have made a short list of things you should prioritize in order to reach ilvl 7500 as quickly as possible when you hit lvl 70.
Below level 70
1. Obtain an Epic Companion from Auction House and fill other slots with Rares. Buy or Refine Runestones to Rank 7+ and buy ilvl 400+ Companion Gear for the Companions that you usually summon (Rarity of all Companions effects your item level, however only summoned Companion needs Runestones and gear) (companion rank does not effect ilvl). Guild events and quests are a good way to get Runestones if you have helpful friends.
2. Obtain an Epic mount if possible and fill other slots with Rares (or at least Uncommon if you really are low on AD). Fill all Insignia slots with Rares or Epics (all mounts and Insignias effect item level). Events are a great way to get relatively easy mounts while having fun. (See Siege of NW link below)
3. Buy Dragon Bone armor from AH if you’ve got the extra AD laying around (Small chance to drop from Dragon Raids). This gear levels with you all the way to level 70. Last time I checked these are not incredibly expensive.
1. Buy ilvl 345+ gear from AH (certain pieces you can get for pretty cheap, just keep an eye out)
2. Buy Protector Artifact set (neck, belt and artifact)(usually cost just a few K ad)
3. Buy Drowcraft shirt and pants from AH
4. Complete Spinward Rise campaign for Artifact Weapon
5. Refine Rank 5 to Rank 7+ Enchantments and Runestones if you havent done so already, or buy Rank 7+ from AH
6. Obtain four Artifacts (quests and campaigns should give you these)
7. Begin refining Artifact Equipment and Artifacts if you haven’t already
Hope this helps!
Other links you may find helpful for gearing up: