Design Pattern for a recommendation engine

The requirement is to design a solution for a product where we parameterize objects based on relevance on different factors.

For Example, let us say we have a list of activities. Each activity contains factors which store its relevance for that factor. Factors could be something like Male, Female, Married, Single, Divorced, Teen group, etc. So a given activity will have a particular relevance rating for each factor based on how useful the activity is for that group of people

For each user, a list of activities need to be displayed based on the user's personal info(like gender, marital status, age, financial_status, no of pets etc) and the relevance factors for each activities.

How can I go about designing this system?

I'm not asking for the solution. I'm just looking for something to get started with and then build on it