Food, Water, and Money

Must Christians practice water baptism? Must we observe the Lord's Supper? Must we tithe?

References:
Gen. 14:17-20, Num. 18:24, Deut. 14:22-29, Malachi 3:9-10, Mat. 3:11, 23:23, Acts 2:41, 8:38, 10:48, 11:16, Rom. 6:14, 1 Cor. 10:16, 11:20-34, 16:2,8, 2 Cor. 8:12-15, 9:6-7, Col. 3:17, Heb. 11:29, 1 Peter 3:20-21