^ Yes very good idea, but THF (C-) actually has an even better bow skill than warrior (D)
RDM can use bow skill also (D).
I would suggest level either WAR or RDM to 18. Than once you do lvl 18 quest to get sub job, use THF to lvl 30 (with the WAR or RDM sub).
THF has best bow skill out of those three jobs plus they make the most money. And everyone says the worst thing about RNG is how expensive they are to play so you will want all the money you can get. Once THF reaches 30, become a RNG/THF
Also, RNG best melee weapon is dagger (B-) and THF (A-), WAR (B-) and RDM (B) are all good with a dagger so you can be raising your dagger skill as well in preperation to play RNG.
THis is educated guessing...I've never played. But it seems to make sense to me. Just my two cents.