Well, since the goggles can take 2s-6s, and have XT60 connectors, I would recommend seeing if you can find a 2s-3s battery, 1800-2200 mAh capacity, with XT60 connectors.
Reason for this is fewer cells mean lighter weight, and this IS going to hang off of your head; the more weight you have, the more it feels like it's pulling at you. Going for a 4, 5, or 6 cell battery is adding more weight and more cost, with no performance increase for the goggles.
As for the FPV video transmitter, you probably have a lead that came with it that will connect up to the video transmitter board. Simply take the end that doesn't connect to it, and solder the red and black wires to the red and black wires on your battery leads on your speed controller. Looking at how the simple FPV video setup was done in the July 9, 2014 article, they just soldered the video transmitter lead to the ends of the XT60 connector, black to black, red to red. That should do it for you..