footstraps first or second is really a personal choice. Personally i hate doing it and i avoid it at any cost. First i give the sail a few pumps depending on the wind, then i hook in asap and then i move back and step into my straps. I've seen a few people do it differently, who first go for the footstraps and then hook in but I teach all of my students the techniques for harness sailing before i teach them footstraps simply because the harness ables you to use bigger sails and surf longer sessions whereas footstraps mainly increase speed and boardcontrole.
I've read a fair bit about footstrapsailing when i was getting into it and everyone has different advice. What you should do is try them, see how your balance is and once you've found your pref, stick with it. I've gone with the classical front foot first because in the beginning it's easier to move back and put in the front foot and simply sail with one foot in the straps rather then the mandatory 2 you need in the backfoot-first setting.
in the end, windsurfing is a feel thing, technique comes automatically through experience.
keep it fun!
Haiko, AKA crazychemical