I found it very useful to do two things in this game.
1. Send friend requests to everyone you visit. I now have over 300 friends and visiting them all each day gives a massive boost in exp. If all you are going for is level 15 this is a quicker way to get there.
2. Store the cottages, tavern and paths and build markets. Build the first market, upgrade it once, then save for another. Although they cost 3100, each market bring in close to or more than depending on upgrade 500 coins every 4 hours. I am now at five markets, giving nearly 3000 coins plus lemonade, pies, biscuits, eggs every four hours.
I've been playing less than a week, am level 13 have 20,000 in the bank with the castle, two mines, two lumber a watch tower and an (unfinished -need those enchanted beam ) magical well.