I would pay platinum for
Pets
Mounts

and i'm ok with doing it for the moderately priced
revives
timer resets
skill respec
elixirs

I would also pay a monthly fee for as an option if that meant fixing some things like consignment store taking payment on true consignment, not on posts...

for right now the best thing to spend platinum on is Gold so that you can afford the CS costs, buy good gear, and feed your sick and dying pet