As the title states, what is the best way to get income from mobile games? (taking into consideration that creating the games only costs a lot of time and the games are relatively simple)

As I see it, there are multiple ways of getting money from mobile games,

1. Selling them for a fixed price (seems like a high threshold for potential buyers)
2. In-game purchases (I can imagine this only works for several types of games, I don't see this working well for monopoly unless you like really fancy hotels ;)
3. Ingame advertisements / sponsorships

Which way will most likely bring the most profit?