As stated in this thread, another user I am aware of, a friend of mine, was creating an account and they could not complete the process because it was not allowing them to purchase their clothes all at once.

When they went to go buy the gloves and winter cloak it would work, but when they selected "3 plain black robes" it told them they should buy their supplies first. I don't know if this is an issue any other players had (or if it was something that player was describing) but it sounded similar. Thanks!! xoxo

I've had this issue before, with my iNPC, who could not purchase a copper scale. It was fixed by reloading the page.