Definitely do the spine first. Then you can either break thread & go back to beginning, echo or stitch backwards down your spine to get back to the beginning to do feathers, or if you are especially talented, you can quilt the feathers beautifully whether going up or down the spine (I'm not there yet).
If the free videos help you enough, definitely start with them. I could never make heads or tails of how to quilt feathers until I watched an iQuilt class with Green Fairy Quilter (Judi Madsen). I liked the class so much after being given free access to the beta version for nearly 2 months that I actually paid to buy the regular version of it so I could refer back to it over & over again.
https://www.iquilt.com/course/quilti...-a-difference/