This is a hard one to answer without insulting or hurting people. First I would say that the one's who teach the prosperity that I have heard are false preachers on tv. I am amazed at how they say things like "sew a seed for the kindgom and God promises to bless you beyond....blah, blah, blah" They of course take passages from the Bible out of context or overly emphasize them. The vulnerable people who listen are the ones I feel sorry for. Some are shut ins and have not ability to attend services where they can hear the truth, some are desperate poor souls seeking help and some are just gullible. The ones that I have a hard time with are the "sensational junkies" who have to be promised big things, great healings, great lives, great services" to remain faithful. If they don't hear what they want they leave and say a place was dead and move on to one after another until they find one that entertains them enough. Christianity to be sure is a blessing and can bring about help from God, answers to prayers, peace beyond understanding and even turn some lives around financially. Not all can handle wealth and continue to live as God would have, he knows what his children can handle and what they need. I know some folks that are sincere in their beliefs and say they are true Christians but they speak of their walks as if they were in an amusement park. The church service had to have the spirit flowing mightily, the music had to move them to a higher plain, people had to speak in tongues, prophets had to reveal God's special message to them, they were promised they were on the verge of a great break through. Everything has to be a great over emotional experience or they deny God being in it. I believe when people say God has blessed them but I don't believe everything God does for me seems to be great. Some of the things that God does for me is keep me humble, allow me to do without because it wouldn't help me, let me pay for my mistakes and so on in order that he remains God in my life because I have asked him to always keep me in a position that I never rely on myself, wealth or any man. God help those who use his word for their gain or deny him unless he meets their terms. We are to give God his due and that means time, money and our lives but not with the expectation that he is going to give us wealth. Paul says with food and clothing be content. God has blessed me and the more I give him the more he gives back but if he cut off the blessings tomorrow (like Job) I would still worship him in spirit and in truth and not give up on him. What a man sews he will reap but don't think that only applies to money. You might give 100 a week to your local congregation and may reap faithful children, a good job, a loving friend or other areas you aren't aware of.
Give it all to God as in all your heart, soul and mind and he will bless you. He will let you know how much to give, when to give and who to give it to. He will also assure to meet all your needs.