Similar to what Roquey said, I'd probably go with marker then hopper next, because they're the big two that will affect your game (Air tanks in terms of overall performance are fairly generic -*excluding efficiency/weight etc which come down to fine tuning and personal preference...*- ) and can also be rented from most fields.
The same goes for "accessories" such as Gloves, which can be left until last, if needed at all, although i hate being shot in the knuckle!
Similar story with pod packs and pods, as they are fairly low-cost and don't really have as much of an impact as the other items on your list, but will still be important at events if you can't be bothered with the hassle of rending equipment.
Finally i'd go with the kit bag if you can wait. At first i used a rucksack, now i'm on a cheap and easy duffel bag i got from my local sport store. As much as i hate it (it's heavy, uncomfortable and has no wheels) It fits everything in it, so i'm happy with it for now, as i can do without parting £50-100 for a Planet Eclipse Kit bag, as much as i'd like one
By the way, nice choice of mask
