What rep is best for us to get first at 90?
After that, you have two paths to choose. You can run heroics until you are geared enough for raids (460 for MV, 470 for HoF and ToES, 480 for ToT). Or you can take the long painful path and grind out Golden Lotus to at least revered so you could then start the grind on Shado-Pan and August Celestials so you could buy the 489 valor gear.
Also, Dominance Offensive is a good reward for time spent run. Klaxxi gives you a 489 epic ring for an easy quest and two pieces of 489 valor gear, DO gives a couple pieces of 496 Valor gear.
Sunreaver Onslaught gives some nice gear. When you get over 480 average iLevel you can do ToT to get the best valor gear, from Shado-Pan Assault (and you can get the first piece at neutral, a 522 neck, so go do that with your first 1250 valor).
My suggestion would be Klaxxi and DO, plus a lot of heroics, then run raids as you raise your iLevel. Do Cloud Serpents if you want on the side. When you can survive the island, do SO if desired, and get to 480 to do ToT.
Spam dungeons until you have 460. Run LFR till you have 480. Bank VP so when you can run ToT LFR you can dump VP on 522s. Only bother with spending VP on other reps if you're going to cap, or it possibly when you're a couple ilevels from 480, and want to get it in before the week is up (and even then I would just buy it, not use it, and refund it every 2 hours)
Only real dailies you need to do is the isle dailies.
You are a tailor and enchanter.. you will need to rep for your enchants and the bag. Those are the reps you will need to work on long term. I'd suggest tillers\farming as you can rep with that now and it helps with the mountain of dailies you aren't going to want to face.
As Varlth stated the valor gear below 522 is obsolete now so limit what you spend there.
The only rep gear that you might consider spending valor on would be a ring (probably the 496 one from the kirin tor offensive/sunreavers) and only because before ToT, there's only one epic ring available to you through LFR. In fact, you can look at my rings. Still rockin a blue, baby. Even then, your valor budget is going to be so short in these first few weeks, that I wouldn't do that, and save it for 522 gear from SPA. (edit: so I just saw in Cocheti's post that you can get a 489 ring fo' free from klaxxi at exalted, so definitely take that route... and I might have to look into it, myself!)
My advice for a fresh 90 looking to do PVE is as follows:
1. Go to to the Isle of Thunder at least once a week and kill rares until you get a Key to the Palace of Lei Shen. Run the solo scenario and stay in the first room, avoiding traps and looting as many chests as you possibly can so you can get as many Elder Charms as possible (for bonus rolls on 5.0 bosses). Also do dailies there until you hit honored with sunreavers so you can buy a 476 belt for gold (not valor!).
2. Do Sha and Galleon weekly. Use bonus rolls. They can give you 496 gear.
3. Do enough dailies (25) to do the quest at Shrine for Mogu Runes of Fate. You can get 3 a week and you can use them for bonus rolls on 5.2 bosses.
4. Kill Oondasta and Nalak weekly. Use bonus rolls at your own discretion (they can award 522 gear), but note that your supply of Mogu Runes isn't as high as your supply of Elder Charms.
5. Grind heroics till you get a 460 ilvl.
6. Talk to Wrathion and start the legendary questline before you start running MSV LFR.
7. Run MSV LFR and use the crap out of your bonus rolls to get your ilvl up to 470.
8. Rinse and repeat with HoF and ToES LFR to 480.
9. ToT LFR, you've made it. Now a guild will consider taking you for real content.
^ that's probably the fastest way to gear up for PVE content that I know of, and it involves very little rep grinding, outside of a few sunreaver dailies for that belt (optional, tbh) and the 25 dailies a week for your Mogu Runes. And really, you could be pet battling for those lesser charms.
Alternatively, you could grind battlegrounds for malevolent gear, since that has an even higher ilvl than heroic 5 mans, but that's lame.
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