Mining an hour for 6 stacks of Adamantite ore, prospect & sell the gems = about 170g profit on my server.

- or -

Spend 5 mins in town to buy 6 stacks of ore & the other stuff, follow this guide = 45g profit on my server. Spend that hour you spent mining, and make 500g+ instead.

But you are market-capped on exactly how much blue/green gems and LPS you can push through in a day, so it's even smarter to take a little while to load up the AH, then head out and do some gathering, daily quest, etc. Personally I find flying around in circles boring as hell so I only gather stuff in instances or if I find it on my way to somewhere, pretty much.