You probably won't be stuck there for very long. Especially early on, you get stronger pretty quickly as you level up various things.
The best places to farm are:
1) whichever event dungeon happens to be active at the time,
2) hidden dungeons and the convoy at the end of normal campaign maps,
3) convoys in daily world bosses and daimyo world bosses,
4) daily challenges, and
5) opponents that drop gold tickets and curse fragments on map 6-3 and later
Not necessarily in that order. Some event dungeons give such terrific rewards as to be far and away the best place to farm while they're active. Others don't. I haven't yet seen any event dungeons that are pathetic enough to be pointless, other than when they were trying to charge koban just to let you play.
You definitely want to clear the convoys in the world bosses, as that's your main source of rations that makes it even possible to farm other maps.
Daily challenges are primarily notable for the gold ticket as a three-star reward for the last opponent on the map, but less valuable if you can't get there. The Monday and Tuesday daily challenges are massively easier than other days. The final opponent on Monday also gives you a chance at a precious universal EVO card.