Extreme speed would go first. Extreme speed has a +2 priority, gale wings gives flying type moves +1 priority. The way priority works is, if each Pokemon uses a 0 priority move the faster Pokemon goes 1st, BUT if a Pokemon uses a +1 priority move they will go before a 0,-1,-1 etc. priority move. It could be the slowest Pokemon in the game using quick attack on a maxed out speed ninjask with 6 speed boosts, but the priority move goes 1st! Hope this helps!
