After playing some games, I've come to the conclusion that the ingame shop is completely unbalanced. Because of the way the shop works I optimized my gameplay around playing with parties instead of armies. Right now I can't even think about playing without using the shop.
How to exploit it:
1. Imba blitz support: You conquer a city with your band of heroes. In the same turn you enter the shop and buy/use/stock up potions to heal your party and carry on. Let's just forget about con/HP buff which makes this even worse. A nice party can trample cities with 10 large units.
2. You see an army approaching: You can use saved funds in the same turn to equip heroes stationed there that provide simple passive bonuses. profit.
3. Ele is extremely rare! yet on the same turn you research the tech you can give your hero party full ele gear!! It's like the shoppers were waiting the kingdom announcement for the research to open their shops!
4. You build a new city in the middle of nowhere to buy/sell stuff and heal your armies. You can also buy top tier magical items in an empty village!!
1. In newly conquered or built cities, 10 turns must pass until the magic shop opens/reopens.
2. City level should affect what tier of items are availiable.
3. There should be a global stock of items available per turn per kingdom. 1 potion per turn max 4 stocked, 1 legendary plate per 5 turns max 1 stocked and so on.
4. Add more ele in the world and have the shops accept the resource instead of gold, top tier equipment is too strong as it stands don't give it to the player for gold.
5. A hero can enter the shop only while he/she is in a city. There are no shops selling magical items on the borders of any empire.
6. The hero *orders* items in the store. The Items arrive 1 turn later in the city they were ordered.
The Idea is to make the game less prone to sudden fluctuations in the power levels of factions. Conquering cities must be slowed down to give enough reaction time for the player/AI. The player must make ample preperations and plannning.