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Check the items they took off of you and sent in the mail.
I only did one toon with the upgrade.
The Greens they put on the toon was half of what the toon had on.
Also look at the AH for some items that others have posted. Look for cheep greens and blues to get you through the quests for better gear.
Check your map for World Quests that would give upgrades as well.
Anyway good luck…
Running into issues with multiple same level mobs when unprepared is pretty normal while leveling. Class/spec balance while leveling also isn’t very tightly tuned, so there can be a fair bit of difference in difficulty just based on what class and spec you are playing as well.
For leveling, the best gold investment for gear is going to be the heirlooms as they’ll last longer than any BoEs you can get off the AH. But, in the end, it’s probably more about getting familiar with your character’s toolkit and learning what situations they can handle and when they should be running!