The most apparent one is bag/bank space. Buying additional slots is by character and not by account, but all crafting materials have their own separate bank they fill. You can convert ingame gold to gems(The Anet currency) to buy whatever you want, and vice versa. You can use real money to buy gems to convert to gold, or use real money to buy gems and buy things off the ingame store like unlimited use gathering tools, boosts, outfits, ect. Everything in the cash shop can be bought with ingame currency by converting gold to gems.
There is no pay to win.
The only real money I have spent in GW2 is for an outfit and I have been playing on and off since launch.