Should i buy armor and weapon?

Hey i am hunter level 40 but my gear is kinda low level. I am confuse, should i buy weapon and armor or just keep farming to get better loot ?

https://i.imgur.com/DEIHrGP.png

keep xping, you'll eventually get decent gear that replaces nearly everything when you reach outlands (lvl 58), worrying about gear before 80 is often not worth it

What about gear that i am no longer use, should i sell it to npc vendor or AH?

You can't sell "used" gear in AH, only items that you dropped but never equipped. So you should sell your "old gear" to vendor for a few extra gold