I haven't spent any money beyond the box price yet. I'm a "smell-the-roses" kind of player, though I play too much to really be considered "casual" if you are talking just time spent logged in.
Having said that, I'm just now getting to the point where I am considering two more character slots so I can have one toon of all seven of the professions I'm interested in. I'm also just now getting to the point where I'm considering another bank tab, because up to now I've been able to manage my inventory well.
But those are the only things currently in the cash shop that interest me at all. I refuse to pay real money for anything that only gives me a chance at something. I want to be able to weigh the gem cost against my perceived value for the item, then decide whether to buy it. Anything that gives me an RNG chance at something has absolutely no value to me.
There are other things that would get me to spend more real money on this game.
1. Mounts - Yes, I know people hate this idea, but a 60% speed boost, land only mount would be worth money to me. I like the feel of riding a horse in a fantasy game. And it would put me out in the world, crossing zones, more than the current waypoint system does. I promise not to complain when I get dismounted by mobs when I try to ride through them and they engage me in combat.
2. Automatic Town Clothes when in town - As it is now, I don't have an interest in town clothes, because I don't want the hassle of switching to them every time I enter a town, only to have them disappear as soon as I take 2 hp of falling damage. Another option would be to give me the option for Automatic Town Clothes when not in Combat. I'll wear them even more, and see them as worth purchasing.
3. Attractive Town Clothes - Right now we most have gag clothes. Chef's hat, aviator glasses, boxing gloves.
I'd like other options beyond my starter set of Town Clothes that I can wear. Things that are attractive and make me distinctive when out of combat.
4. Name Change Contract - Despite rumors, this hasn't appeared in the CS yet. I have a level 65 character with a name that people pronounce differently than intended. I've since come up with something far better, and would like to change to that. It'd be worth 800 gems to get a new name without having to level from 1 again.
5. Awesome dance emotes - I'd be willing to sink some cash into some cool dances.
6. More stuff that is Account wide, instead of character bound. As is probably clear by my intro, I tend to make and delete a lot of characters. I'm not going to put real money down on for something that is going to disappear if I choose to delete a character, or simply lose interest and stop playing that character.
These are all ways ANet could get more money from me without adding gear tiers.