If you are saying what the money or time was spent on, i.e., the activities
engaged in, use the -ing form.
If you are telling why the money or time was spent, i.e., the purpose for the
spending, use the infinitive form.
In some cases you can interpret the thought as both the activity and the
purpose, so either one can be used.
We spent a lot of money advertising last year. (We spent a lot of money in
the course of doing advertising activities.)
We spent a lot of money (in order) to advertise last year. (We spent a lot of
money for the purpose of doing advertising.)
I would not use spend with efforts. I would use expend.
He expended a great deal of effort [to help me / helping me].
https://www.englishforums.com/English/SpendMoneyDoing/zxdbd/post.htm
101年學測考古題。
Although Mr. Chen is rich, he is a very stingy person and is never willing to
spend any money to help those who are in need.