How to predict consumer purchase in next 6 months?
This is a forecasting problem, you are predicting a value in the future for a group of people which is the day they would make the next purchase. Sure, you would need the last time each person has bought something ( that's your target ) , periodicity of purchases;number of times that person bought something,obviously the id of the person as variables. And those are the things on top of my head, maybe someone who worked on forecasting problems could help you better.

On a second note : this is how you could approach the problem; maybe encode the dates they made the last purchase as date_num 1 to infinity, and each number in this target variable represents a consecutive day starting from a certain date(maybe the oldest date in your dataset). You would do a regression to try to predict that number using every potential predictor and round it to get an integer representing a unique day.