Being a gold member earns you crowns a lot faster than being a silver or free member. Also the maximum number of crowns you can have is 5760 on a gold account, 2880 for silver members and 1440 for free members; if your account is currently at those numbers for it's associated membership you should go to the housing area and buy stuff from the loyalty merchant(tax authority) so that you can earn more crowns.
One of the best rewards to buy with your points is the Gold Ticket which can be traded in the Shadow Haven at Shadeling's Roost(near bazaar zone line) for 7 possible items that no longer drop, such as Guise of the deceiver, and an 8th item that summons a drogmor that is as fast as emp/seru horse. All items besides the guise of the deceiver and the drogmor are tradeable and lore so it's possible to try and "fix the game" so that you'll much more likely to get your drogmor if that's what you're after.
I also recommend buying the stat foods. Hazenfranze and Metamorphic Oatmeal are the ones I recommend if you're a tank class. If you plan on using the stat foods I also recommend getting the metabolism and forage AAs so that you can make these foods last without having to constantly spend you loyalty points re-buying them.