The "firstfruits offering" is a sacrificial offering given from the first of the first of any harvest or increase.  This offering enables the remainder of the harvest or increase to remain blessed.

Romans 11:16.....For if the firstfruit be holy, the lump is also holy: and if the root be holy, so are the branches.

Deuteronomy 18: 3-5......3. And this shall be the priest's due from the people, from them that offer a sacrifice, whether it be ox or sheep; and they shall give unto the priest the shoulder, and the two cheeks, and the maw.  4. The firstfruit also of thy corn, of thy wine, and of thine oil, and the first of the fleece of thy sheep, shalt thou give him.  5. For the LORD thy God hath chosen him out of all thy tribes, to stand to minister in the name of the LORD, him and his sons for ever.​

The "Feast of Harvest" also known as the "Feast of Firstfruits" was one of the national feast that the children of Israel where commanded to observe (Exodus 23: 14-19).  As a born again believer regardless of race or ethnic group, if one has truly received Jesus as their Lord and Savour , they have been adopted into the family of God and have become spiritual Israel.

Proverbs 3:9....“Honour the LORD with thy substance, and with the firstfruits of all thine increase: