There is nothing in the store you NEED. There are things that can make life easier. Rez pots, vanity items, certain mounts, nuthing that you need though.
Being a paid sub and getting the godslayer expansion gives you most raids, pretty much access to every type of mount, AA, top tier raid gear, everything but turan area which you dont need less you want to raid t3.5 or do ashidar fort.