Manage your hate, use Souleater *intelligently* once you get it, try to cure yourself with Drain rather than going "waaaaah heal me". Go for a bit more acc and DEX than you would otherwise - Vision Ring is a nice shiny for example. For food, try Rice Dumplings instead of Meat Mishkabobs, but of course don't be one of those nubs who eats sushi at such low levels that it does nothing.
RNG (Accuracy Bonus = +10 acc) and DRG (Jump for a free hit + TP) are both very good non-standard subs for 20-29 for any melee job, especially a two-hander. Before 20, no sub really offers all that much, so probably the best you could do is WAR (emergency voke or even try full-time tanking since most melees' defense is more or less equivalent at those levels) or WHM (toss a few cures *between* - not usually *during* - fights, so your MP pool is somewhat more useful).
