Where do I buy gathering tools as low-level human?

They're fairly common. There are vendors at just about every village, and a majority have gathering tools appropriate for their area. Just look for the "merchant" tag or symbol.

If you don't see the tools when you first check with a vendor, make sure they don't have them hidden on a second page or something. There are multiple tabs that you can view goods on for some vendors.

Worse comes to worse, check in with a trainer for a crafting profession. They will have all tools for all levels.

If you want specific to around Shaemoor, either go back to Divinity's Reach for the profession trainers, or hop into the garrison building just over the bridge to the east, where you should find Tara.