God doesn't own 10% of what we have, it all belongs to Him. We are stewards of what he has given us. Anyway, while tithing is biblical and, as long as your income level isn't too low, 10% really isn't that much, below a certain point, it might not be practical. It is meant to be a sign of thanksgiving for what you have been given, not a legal requirement. If you give 10%, and it causes you not be able to feed yourself, or you end up harboring resentment or regret for having given it, then you shouldn't give that much. It would defeat the purpose of giving in the first place. Maybe you should try to figure out what you are comfortable with/able to give in order to give thanks to God and take a small but active role in participating in supporting your local church.
As far as trusting God to take care of you, Christ mentions that God takes care of the brids and the animals and in other places mentions that He does not have a place to lay His head. We are to accept that even in the lowest form of poverty, we are being taken care of and God is blessing us. The Protestant idea of "give and God will give back to you in return" is backwards and the complete opposite of "giving thanks to God for what you have already received".