I'll just echo what Lionx said. /WAR will be the best overall sub. Once you are past 60 make sure you have /THF available for SATA. Also at 60 you become a pretty decent soloer with /WHM especially and /RDM is okay as well.

/NIN is a good sub for all melees to have available. There will be certain places where it'll be useful like Lionx said. One in particular I can think of is CoP Mission 6-4.

Also I don't want to be a spoilsport and I definitely think every job and race has their place but be prepared to grow a thick skin as a DRG. Your job will be the butt of many jokes and invites will be slow. Learn to do the most with your time LFP and it might be slightly less frustrating. And Good Luck!!