When you have completed your third zone, you should be nearly max level, but you still have work to do! Head back to your faction hub and complete the last foothold quest to unlock your fourth mission table champion. After, you will want to do your newly available invasion missions for your faction. This quest chain is one that will be time gated by reputation levels earned with the 7th Legion for the Alliance and iThe Honorbound for the Horde. Complete as many quests as you can and then finish up your leveling with side quests you may have left in previous zones as necessary.
Go to https://www.tradeskillmaster.com/pets/compare to compare prices of different servers. I’ve done this a lot, and I’ve bought pets for a few hundred gold on a server, transferred it to my main server and sold for 10k gold and more. You also need to buy cheap pets on your main server to transfer to other servers so that you can build up a bit of gold on other servers so that you can buy pets.
Most people come here not to read walls of text, they look for the better-rated strategies that match their pet collections, copy&paste stuff they need to import into their addons and only come back if something goes horribly wrong and then mostly to find help in other peoples' comments who also struggled or to find a different team/strategy: I don't think many people wanna read about stuff that already happened to them, they mostly want to see solutions and it's the best way to have them in a well-optimized strategy&team already.
Your server population may determine how much profit you can make. Lower population servers generally have lower prices in the AH as there is less demand, but rare items or recipes can really make a profit as they are harder to come by. Higher population servers have a higher demand. However, they are more likely to have a flooded market, which makes items hard to sell, especially in the case of low-level gathering professions.