Which dig site should I buy?

1. Precious dig site costs 100 coins: harvest 15 coins every 1 hour (net cost of 85 coins)
2. Mysterious dig site costs 250 coins: harvest 25 coins each 4 hours (net cost of 225 coins)
3. Curious dig site costs 1800 coins: harvest 200 coins every 8 hours (net cost of 1600 coins)
4. Exotic dig site costs 7500 coins: harvest 800 coins each 24 hours (net cost of 6700 coins)

Building sites is a great way for making more coins.

Tips:

• Precious sites are very energy consuming and harvest from 1 in 1 hour. In 6 times been clicked already paid itself and after is all profit. These are the most profitable ones by hour.
• Mysterious dig sites you need 9 clicks (36 hours at least) to cover the buying cost. Also, due to this cost, you can buy 2 precious sites and the income each hour will be 30 coins (and recovers quicker the buying cost)
• Curious dig site has the advantage that overnight makes 200 coins to harvest in the morning. So, if you have some extra coins to invest, it is a good investment.
• Exotic dig sites are too expensive and not worthy.

Best advice is: 

- buy the 100 coins sites (harvest in 1 hour) for harvesting during the day and

- 1800 coins site for overnight (harvest 8 hours).