As a FFXI Dark Knight, this is extremely familiar territory and thus, this is the golden rule in this situation:
"If you aren't hitting the target, you aren't doing damage."

Such a simple and obvious rule, wouldn't you say? Therefore, make sure you can hit the target before you focus on doing more damage. After all, you can have enormous power, but if you can't use that power then there's absolutely no point to it. Focus on your accuracy until you can hit often. Then, and only then should you worry about how much damage you do.

As far as gear is concerned, use the gear that allows you to hit the target often and hit the target hard. Obviously if you can hit the target often, go with whatever gear raises your damage. If you can't hit the target, go with the gear that raises your accuracy.

After that, choose the food to eat. Still not hitting the target? Eat ACC food. Hitting the target consistently? Eat ATK food. So when all is said and done, your party will be glad that you brought gear and food for both situations.