You will get a ton of purple runes. Pick them up and combine them into one big fat rune and level up the ones you are using. The higher the runes the more powerful your heroes are. They are wasting your coins by sitting there in the chest. Your screenie shows some level 4 and 5 purple runes on your main. Level those up to 8 or 9 and you will see major power increases. When you buy a rune you pay 8K to 60K each. If you sell one you only get about 2,800 for them so you are losing a ton of coins selling them. Trust me when I say combine the purples, blues and greens. Feed those to the runes you are using. Replace the purples with the gold ones you get.