I’m not poor but this always helps everyone. Wait for a while before you buy the thing off your shopping list. Wait for a week and reconsider whether you indeed need it.
If the answer is still yes, buy it. It is a must do for expensive things. Never break this rule for any massive purchase like a car or something!
If you comply with their interests, nothing. Once you do anything that even looks like being against their interests, they use this data. There are programs of called DARPA LifeLog which literally logs everything. They even create DeepFakes based on the data they collect, ofc, not officially.
Yes, never give any data more than you need to give and move towards free and minimal software.