The simple answer is to spend money on leaders who will raise up more leaders (or facilitate that process).
It’s the principle we see again and again in the bible.
The glory of David’s earthly kingship was not his army of men, but his men who each led their own armies (a bit like Jethro’s advice to Moses). Jesus invested in the 12, sent out the 72, all because the harvest needed workers. Once the gospel exploded out of Jerusalem (Acts 8) each disciple became leaders of new things. The kingdom grew. Paul invested in Timothy, who was to entrust the message to faithful men, who would go and entrust it to others.
But the description of the church “building one another up in love” in Ephesians 4 is most helpful. The church’s earthly goal is self-growth; both numerically and spiritually. So leaders like evangelists, pastors, teachers (even the apostles and prophets of the time) were meant to help the members of the church grow each other.
So, where should a church spend its money?
It’s should invest in people who will lead, teach, mentor, entrust other people to be leaders within the church, for the growth of the church.
There will be times or seasons when a church needs to invest in ways to increase the efficiency of those people; by providing an office, or a building, or a database, or a website, or a publishing house and books.
But the facilitators must know their place in the pecking order.