For those who have some spare coins for levelling up, following is a comparative calculation showing the most economical way of doing it (if not interested with the details of calculation, just check the comparison list at the end of this post please).
1st way:
buying the most expensive thing from store (which is a cuckoo clock now sold for 18500) and selling it back with a small loss;
you pay 18500, you get 15000 at average for selling back. you get 111 yopoints for buying it (it looks like a good deal)
18500-15000= 3500
i.e. you spent 3500 coins for 111 yopoints in real. so:
3500 / 111 = 31.53 coins per yopoint
2nd way:
buying tons of cheap items from store (50 coins plants or similar things) and selling them back to the store (you may get more by trying to sell them back to yovillians but it will probably be a great loss of time);
you pay 50 coins for 4 yopoints, and you get 15 coins back for selling each item to store. so by spending 5000 for buying and getting 1500 of it back from store, you r spending 3500 coins and earn 400 yopoints. so;
3500 / 400 = 8.75 coins per yopoint
3rd way:
having meals from the popcorn or espresso machines. you get 1 yopoints and pay 5 coins for each meal from the machines (i need a confirmation on the meal prices of the machines tho, i m not sure if its 5 or 10 coins per meal). so by spending 3500 for the meals, you earn 700 yopoints and thus;
3500 / 700 = 5 coins per yopoint.
Results:
1. buying collectible and selling back —> 31.53 coins per yopoint
2. buying small items and selling back to store —> 8.75 coins per yopoint
3. havin meals from the machines —> 5 coins per yopoint WINNER!!
And just a quick note for the ones who chooses money spending for levelling up in the game. final level that can be achieved is 50, and you need to earn 32200 yopoints for getting to that if i m not mistaken. so;
32200 X 5 = 161 K coins
is the total amount you have to spend for reaching level 50 (if u prefer the cheapest way explained in the above posts). it’s still a huge sum for most of the players, so i suggest you keep visiting friends, playing games, going to factory regularly etc. sooner or later you will get there, even though you don’t have the coins.