Does Ganking allow a unit to move an extra time? When can I use the Ganking ability?

No, Ganking is an extra way to use the standard move. Normally, when a unit uses the standard move, it can only move between base and battlefield. If a unit has Ganking, it can also move between two battlefields. You can move units with Ganking alongside other units that are moving with the standard move, as long as the destination is legal for all units moving as a group.

Related: Rule 144.4.c.1, Rule 810.1.c.3