How to giving 1 point per every 10 dollars purchase using scoring

Custom activity is the best option IMHO.

Thanks Brendedn.

Actually we get the data from an API. So if customer purchase amount was 5,000$ system generates 500 custom activity. Then gives 500 points based on rule that gives 1 point per these activities.

Is it OK? And should I worry about performance or something like that?

Sounds as if you are generating your points based on the wrong activity. The activity should be the purchase, not the dollar amount of the purchase.

In fact, suppose we are going to give the contact 1 point for every $1 of their purchase after receiving the contact's purchase information from the Third party API.

If we use the purchase activity defined in Kentico, we need to define a new rule for every $1 increase in price, and thus we need to define 100 rules to cover amounts from $1 to $100. Defining and managing this number of rules will be difficult and time-consuming.

With the purchase you know the dollar amount. Create a loop that iterates through each full dollar in the purchase price and apply a point. You don't need a custom rule or activity. At best you have a cross-reference table that states how many points per dollar you apply to a person.

For example if you have a purchase activity and the purchase price is $37, your activity captures the purchase and loop through the $37 and apply 37 points.