Equipment for the Divine and Fallen can be bought from the guild shop in their respective sections of the guild halls.
Divine angels who choose to show their wings will often need to get their armour either modified, or reforged. Both of these things can be performed by Michael.
For those who are short on cash, or desire to use something better, there are several vaults where equipment may be stored by others in the guild, the most prominent of which being with Tyraeus.