Offerings of the firstfruits of the yearly harvest were required under the Old Covenant made with Israel at Sinai.
Leviticus 23:10-17 Speak unto the children of Israel, and say unto them, When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest: 11 And he shall wave the sheaf before the LORD, to be accepted for you: on the morrow after the sabbath the priest shall wave it. 12 And ye shall offer that day when ye wave the sheaf an he lamb without blemish of the first year for a burnt offering unto the LORD. 13 And the meat offering thereof shall be two tenth deals of fine flour mingled with oil, an offering made by fire unto the LORD for a sweet savour: and the drink offering thereof shall be of wine, the fourth part of an hin. 14 And ye shall eat neither bread, nor parched corn, nor green ears, until the selfsame day that ye have brought an offering unto your God: it shall be a statute for ever throughout your generations in all your dwellings. 15 And ye shall count unto you from the morrow after the sabbath, from the day that ye brought the sheaf of the wave offering; seven sabbaths shall be complete: 16 Even unto the morrow after the seventh sabbath shall ye number fifty days; and ye shall offer a new meat offering unto the LORD. 17 Ye shall bring out of your habitations two wave loaves of two tenth deals: they shall be of fine flour; they shall be baken with leaven; they are the firstfruits unto the LORD.
Israel failed to keep the Covenant and God promised a New Covenant.
Jeremiah 31:31-34 Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah: 32 Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD: 33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people. 34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
This New Covenant was inaugurated by Jesus Christ.
Hebrews 8:8 For finding fault with them, he saith, Behold, the days come, saith the Lord, when I will make a new covenant with the house of Israel and with the house of Judah:
Hebrews 8:13 In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away.
Jesus Christ is the mediator of the New Covenant; the Old is no longer in force.
Hebrews 12:24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.
Those who believe the gospel and are baptised into Jesus Christ are not required to offer firstfruits. The firstfruits prefigured the firstfruits of the spiritual harvest. Jesus Christ was the firstfruit to be raised from the dead and the full harvest is in the future.
1 Corinthians 15:20-23 But now is Christ risen from the dead, and become the firstfruits of them that slept. 21 For since by man came death, by man came also the resurrection of the dead. 22 For as in Adam all die, even so in Christ shall all be made alive. 23 But every man in his own order: Christ the firstfruits; afterward they that are Christ’s at his coming.
Christ was raised on the first day of the week ‘on the morrow after the Sabbath’. He was without sin so the offering was to made without leaven. This was followed 50 days later by Pentecost. The anti-typical Pentecost saw the outpouring of the Spirit upon the apostles and the opening up of the gospel to both Jew and Gentile. This is represented by two loaves made with leaven.The apostles and early believers who spread the gospel are also described as ‘firstfruits’ but baked with leaven. They were not without sin but accepted by God, having their faith imputed for righteousness.
James 1:18 Of his own will begat he us with the word of truth, that we should be a kind of firstfruits of his creatures.
Romans 4:5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
The final harvest, represented by the feast of tabernacles, will occur when Jesus returns to raise the dead and establish the kingdom of God.
I hope you find this helpful.