Welcome fellow Leviathan player. Good suggestions above but i will say unless you have a group to run with you queue times as dps can be rather long for lots of the content. That is where being a healer or Tank you would not need to wait so long.
Ninja, Bard and Dragoon are all 3 good jobs that bring decent damage and great utility and groups always want at least one of them to raid.
Ninja with mudras and depending on your connection can be annoying at times but Bard has always been the best support while doing very good damage so that may be the job for you.