Prosperity Theology is built on a wrong basis: that we are owners of what we have.
God created everything and owns everything and we are just stewards of what He has allowed us to have which are to be used for His purposes. The moment we take control and use them for our own use, like giving to God and expecting Him to give more back, we do two things:
We usurp His authority over the things we give this way
We can no longer use them for the purposes for which He gave them to us to use for.
They also become an idol to us as we place more emphasis on that and our use of them and ignore the fact that God has a purpose for us to use them for and we are not using them for this.
It is also ludicrous to give God back what He already owns and expect Him to give you back more than you gave Him.
There are two problems with supposed giving:
You are giving Him back what is His so He is not being given anything you own or He does not own
You are sacrificing something He wants done with that gift so are not serving His purposes
Satan wants you to have more than God gives you so he can use these things to take up time caring for them that you should be spending on what God has you to do for him with the things you have for Him.
The other fallacy is that God has to reward you for what you do for Him in the way you believe you should be rewarded and not in the way He has prepared for you and which is best for you. The problem is that Satan will try to supply them to use them to divert you from the purposes of God.
God does not have to reward us for anything we do. He is King so we should do what He says without expectation of reward. However, as a loving King He rewards us but not as we desire it but in the way that is best for us.
He real danger of prosperity Gospel; is that we are asking God for things we really do not need because He promises to give us all we need (Matt 6:33) to be a good citizen of His Kingdom. So if you do not have what you believe you need ask:
Does God want you to have it
Are you a citizen of His Kingdom and in a position to receive it
Are you doing His will in that area
What benefit would it be to the Kingdom of God if you were to receive the thing you desire.
It is not for a steward to tell the owner what to do with the owner's goods but to do what the owner says is to be done with them and Prosperity Theology goes against this principle.