Heroes
There is absolutely no need to pay the valuable coins for unlocking them, although that is a possibility. Instead, just play the game and when you reach a specific stage and beat it, you will automatically unlock that hero for free. This is the way to go! When it comes to leveling them up, the only way to do so appears to be by Spending Diamonds. For this reason, it would be best to find the hero you enjoy playing with the most and focus on leveling that one up. I personally found that the starting hero is really good because of its energy skill that removes curses. All the others deal some sort of damage which is useful at taking out monsters, but sometimes those curses can be a real game killer.
New recipes and Crafting
In the crafting menu, you spend your hard earned coins in order to unlock new recipes for you to craft when in missions, but also upgrade existing ones to give you better results. My advice is to focus on the healing and damage dealing items first, the slowly work your way up unlocking and upgrading new items. You don't really have much of an option but work on all of them and focus on the cheaper first because even though you can unlock a better armor, for example, you might not have enough materials to craft it in the game, meaning that it's still the one with lower stats that you will craft and use (since it's better than nothing).
Strategy Tips
Tip 1
The most important thing is to explore the map as much as possible until you have no other places to go and only then start attacking the monsters. This way, you collect all materials that are required to help you easily defeat them.
Tip 2
Remember what each thing on the map will give you. For example, there are items that increase your health as soon as you tap that hexagon (such as the fish) and if you have maximum health, you basically waste a great free health refill. Always know the potential effect of the items in each hexagon.
Tip 3
Don't hurry to craft things and only do so when really needed. Materials are scarce and you can still collect items along the way. Since items share materials required for crafting, this micromanagement thing can help you get a long way.
Tip 4
There is no need to defeat all monsters in an area. There might be a requirement to defeat all the monsters of a particular kind, but if there's none, you can just move on without attacking. Of course, it's up for you to decide if you should do it or not.
Tip 5
Monsters usually guard important items that can help you move forward. The monsters themselves can sometimes give you some sort of a boost or item, so always make sure that you make the right decision, carefully weighting risks and rewards. If monsters are easy to beat, always defeat them all to increase your rewards. If the mission is tough, do some planning and only destroy those who really matter.
Tip 6
Boost your stats when needed using the items in your inventory or by crafting items. They all have limited uses, so make sure that you equip a sword for example when you really need the attack boost - you can't unequip an item and after equipping it!
