Hebrews 5:6-14 - The truths about Melchizedek are for mature people.
"As He also says in another place: “You are a priest forever According to the order of Melchizedek”; who, in the days of His flesh, when He had offered up prayers and supplications, with vehement cries and tears to Him who was able to save Him from death, and was heard because of His godly fear, though He was a Son, yet He learned obedience by the things which He suffered. And having been perfected, He became the author of eternal salvation to all who obey Him, called by God as High Priest “according to the order of Melchizedek,” of whom we have much to say, and hard to explain, since you have become dull of hearing. For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil." (Hebrews 5:6-14 NKJV)
Hebrews 7:1-10 - God doesn't need our money. He owns heaven and earth, and all the cattle on a thousand hills. We are not obliged to give the tithe. Abraham gave the tithe because he recognised how great Melchizedek is. We tithe because we recognise how great Jesus is! When we tithe, it is Jesus who receives our tithe!
Holy Communion is to proclaim Jesus's death. When we tithe, we proclaim that Jesus lives! When we tithe, we are affecting generations. Our tithing blesses our succeeding generations! Even if our descendants don't believe in Jesus, they will still enjoy the blessings thanks to the tithes given by the ancestors. It is no coincidence that some of the most wealthy and inventive people are Jews - some examples are Mark Zuckerberg who founded FaceBook; MGM, Universal Studios are also founded by Jews.