Ahhh.
Blizzard restrict some things for up to 72 hours after payment, and one of those thing can be boosts for reactivated accounts. I guess it’s in case the account is being hacked. It may be that you are still in that period. Try again today and tomorrow. If it still doesn’t allow you, it will be worth checking out then, but I suspect that’s what’s going on.
Surprisingly, Peacebloom seems to fetch a good price on Draenor:
https://theunderminejournal.com/#eu/draenor/item/2447
though I doubt a lot is being sold. Worth a try! Herbing brings in decent gold from BfA herbs, not so much below that. There are a few Ores and Bars that still sell well from Mining, though, even though they are from old expansions.
If you’re gold-aware, Green Bind on Equip gear that drops for you from mobs may being you insane profits. There’s a reason for that … just, if you’re at the AH, and you have some Greens you could sell, check out the prices, and don’t sell them to vendors until you’ve done that.
You can drop Herbing at 120 if you want to take up Blacksmithing again. Professions are now all fractured. You can learn BfA Blacksmithing without ever learning Blacksmithing from older expansions. Decide when you hit 120. 
Levelling has changed. Really changed. We have what is known as scaling. With scaling, all mobs scale to your level. So, for example, when you’re 40, you can go to (what was) a level 25 zone, and you will see the mobs there as 40, and you will get full XP credit for quests there, and you will get level 40 rewards. There are reasons I detest this, but it does have the virtue for you of allowing you a great deal of latitude in what you do: you will not outlevel zones. At all. At least, within limits. The beginning zones up to 10 (or is it 20?) stay for characters up to level 10, but zones above that will increase with you all the way to 60.
So level wherever you like, and do whatever dungeons you like. There will be no quests going Green and then Grey.
However, there is also a Quarantine Special on at the moment: everybody levels twice as fast. So it’s likely you’ll hit 60 quite quickly.
Please do post again if/when you have more questions or want a hand with anything. 