"Wherever your treasure is, there the desires of your heart will also be" (Matt 6:21, Luke 12:34)
I don't think He was giving instructions on where to put your treasure in order for your heart to follow.
I think it was more of a warning, or a diagnostic , to help us examine our hearts.
I think he was saying "Take a look and see where your treasure goes, and you will find out where your heart truly is."
We humans have an astounding ability to lie to ourselves, and tend to justify our actions in order to avoid guilt or responsibility. I think Jesus' statement about treasure was not meant as instructions, but rather a diagnostic tool intended not to let us off the hook, to keep us from too easily justifying things.
I don't think he was saying "put your treasure here" as instructions on where to spend our money and by so doing get our heart to change. I think he was saying, "in order to find our where your heart is, be honest and look at where your treasure goes".
After all, an accurate diagnosis is the first step toward a cure.
Jesus said just prior, in Matt 6:20, "store your treasures in heaven, where moths and rust cannot destroy, and thieves do not break in and steal." Since its not possible to store cash money in heaven, Jesus must have been talking about something other than specifically where we should spend our cash.
He was talking about figuring out what's important.
I think Jesus was saying "examine your hearts, look at where your treasure is, and be honest with yourself about what you actually value and what you really think is important".
As we learn to value the things of heaven, and learn the things that are valued in the Kingdom of God (the things, after all, which God values), those things start to become the important things of life. As our hearts change (by the power of the Holy Spirit working in our lives), as we become new creations in the Kingdom of God, as God begins to replace our heart of stone with a heart of flesh, I think we'll find that we will begin to store our treasure where it matters.
We begin to spend our treasure in ways that reflect our hearts.
Jesus summed it up in Matt 6:33, where he says "seek the Kingdom of God above all else, and live righteously, and he will give you everything you need."
Its not a matter of getting our heart to follow our money. That never works. Our money always follows our heart. Our heart always wins.
To "seek the Kingdom of God above all else", is to learn to see the world through Jesus' eyes, and through the lens of Jesus sacrifice on the cross, and to learn to see the things that God places value on. Its learning to set our hearts on the things of God, the things of the Kingdom, the things that God values.
When we do that, when we re-orient our hearts by learning to seek the good of God's Kingdom, I think we'll discover that we begin storing up our treasure in the things that God values. We'll spend our money on things that reflect where our heart is oriented.
Of course, what God values, what God loves, is us. People.
Jesus' death will set all creation to right, and will achieve reconciliation for all that is in the earth (Col 1:19-20), but it is people that share a relationship with the Father.
We are what the Father treasures. We are His treasure. That's why He put everything He had into saving us. God paid his own life, in Jesus, for us. We are His treasure, and because of that, He is our true treasure.
When we get our worth and value from what God thinks of us, and how much He loves us, we won't get our worth and value from how much money we make, how much stuff we have, or what other people think about us and our worth to them. We will learn to hold onto our money and our "stuff" much more loosely.
When we begin to look at the world that way, learning to love others the way God loves us, what we do with our money will begin to look very different. The things we prioritize to spend on will change. Hopefully, the things of the Kingdom (whatever they are and however you identify them in your life) will become your priority.
Look at where you store your treasure, where you direct your finances and energy, and you will see where your heart is. Take an honest look. If you don't like what you see, if you don't like where your treasure is going, then do something about it.
If we learn what is valuable to God, learn to love and value the things that God loves, I think we will see our treasure begin to follow our hearts to somewhere more meaningful and useful in the Kingdom, and our real treasure will be stored in heaven, with eternal security given to us by the guarantee of Jesus' triumph over the grave.
"Seek first the Kingdom of God".
That's the key to everything.