It will take a very long time (in the order of several years) to even have enough tokens to buy a rainbow from that shop as a free player / without whaling. You'd rather just save up and pay for 6* ticket promos. Yes, you can also earn tokens from 5*/6* clones, but it's not reliable as there's no guarantee you'll get at least a gold pot everytime you roll.

Long story short, it's pretty much intended for big whales.