Dancer is a low personal damage job with high utility revolving around Closed Position, Devilment & Technical Finish. It is currently the strongest of all 3 Physical Ranged jobs in a party that can utilize the utility to its fullest. Here you can find the official jobguide from Square-Enix explaining all skills.
For more information on dancer you can find 2 videos on how to play dancer specifically. A whole playlist of POV's can be found here.
The gearing options for Dancer are very straight forward. Avoid Skillspeed at any costs and meld Crit > Direct Hit > Det. The current Best in Slot for patch 5.2 and 5.3 can be found here.
If you prefer, or are still hungry for more information I suggest you to take a look at my Dancer Guide for 5.X which you can find right here. The guide covers most of the basics for Dancer & also goes in depth about optimization. Please note that this does not include fight specific optimization.
Dancer is a great choice when it comes to the Epic of Alexander as it excells in every phase due to how its kit works. If you decide to play Dancer in TEA make sure to use ilvl 470 gear as it is the best gear available in TEA due to it being synced to 475. As as exception, the Eden's verse Ring (500) is better than any other secondary ring choice. Here you can find the current BiS for TEA. Sadly I do not have any document available for Dancer in TEA but instead I can offer you a POV of my clear which was a Rank 2 at the given time but now dropped to Rank 17!