If you don’t want to pay for them then the only way is the 15 you get every six hours +3 if you watch an ad. You get 15 for the first relationship status level ups and then 20 then 25 as the rank levels up and change. If you don’t mind the grind, you can match with as many people possible and use them as diamond mines to get more from their relationship statuses leveling up. Beyond that then only other way is to pay for more. They are few and far between, but sometimes there will be a decent deal.