Mark 12 has a lot to say about offerings: the evil farmers; taxes; the most important Commandment; the religious leaders; and the the widow’s offering.
Twice Jesus takes aim at the religious leaders who are far from God. He starts on them with the parable of the evil farmers (which they understood to be about them). They were not giving back to God in the way that He expected them to. In fact, in the end of Mark 12, Jesus shares how they have dishonored Him by taking honor to themselves while living lives lacking grace, justice and mercy (with the judgement that is coming to them).
The section regarding taxes for Caesar and the Greatest Commandment speak of giving to God what is God’s. We do what we must to be obedient to civil authorities, but we give to God what is God’s (and we know that the earth is his and everything in it (Neh. 9:6; Psa 24:1, etc.).
We owe God everything, ultimately, and this means all of our worship should be to Him, and to love that which is created in His image.
And giving her all is what the widow did. Many gave from their surplus, and she gave everything she had. Jesus made sure to single her offering out! Isn’t it fascinating that as people make more money, they tend to give a lower percentage of what they make? shouldn’t it be the opposite?