When it comes time to give to God, He expects more than just “some,” He expects your best. We must keep God first in our lives because all that we have and all that we are is really from Him to begin with anyway. God doesn't accept your leftovers, He wants your heart.
Giving to God, is much more than the gift itself, it is a matter of your faith in Him. When you trust Him to provide, giving away what you have is a non issue. It is our doubts or perhaps our sense of apathy to the Lord that makes our gifts sub par.
God observes your motivation. Better not to give than to give with a selfish heart. God wants to be in our lives, every moment. For Him to be there, we must put Him first. He wants to provide for us, but He can’t do that if we don’t trust Him.