If it is really getting difficult in the world map I would say it is time to pause and start farming the lower province to make your heroes stronger. It’s not important how leveled you are or how far on the map you are, it’s about how strong your team is. I suggest farming 5-8 as much as possible to get those backpacks and level up your heroes with the swords and backpacks RT1 and RT2. Also don’t research any levels in the training camp that you don’t need this will help you save food. If you’re spending some I would suggest sticking with the levels 1, 2, 4, 11, 19 and 20. If you’re free to play maybe level 13 but priority is rushing to TC20 and starting those heroes. Use TC4 as recruit storage and later on TC11 as a recruit storage to constantly pump out feeder heroes.
Edit: Here’s a more thorough explanation for recruit storage from GryphonKnight. [Play style] Recruit (RT4/ RT11) & Food (RT13/ RT20) Hoards- Updated 4-14
Here is the Empires and Puzzles Bible with a ton of stats and useful information. I typically use the “best level” tab the most to see where I should farm. https://docs.google.com/spreadsheets/d/19fcmMLrBiXLt0rhnUXE68ONZIPorWS5qUXdKCm-0br4/edit#gid=1209151993