A first-fruits offering in the Bible was an Old Testament practice where Israelites gave the first and best portion of their harvest to God as a way to thank Him for providing the land and blessings after their captivity in Egypt. This offering was an act of obedience and gratitude rather than a promise of future blessing. In the New Testament, the term “first-fruits” is used metaphorically for Jesus’ resurrection and the early believers as a guarantee of future spiritual blessings. Sometimes, preachers today use it to encourage the congregation to give an offering above and beyond tithing with varying conditions. However, the Bible does not require Christians to give a first-fruits offering as a distinct practice. Rather, giving is left to personal conviction rather than church mandate. While giving sacrificially and with thanksgiving is commendable, warnings against prosperity gospel teachings remind believers to give wisely, cheerfully, and in faith, without coercion.
The problem with applying the concept of the first-fruits offering today is that the first-fruits offering was for the Jews for a specific purpose. Nowhere does the New Testament mention that the church is required or even encouraged to give a "first-fruits offering." Like tithing, giving to the church is left up to the personal convictions of the individual believer. There is no blanket policy for giving. As far as the first fruit offering as described in the Old Testament, the church is exempt. Jesus did not come to abolish the law but to fulfill it—including being the first fruit, Himself (1 Corinthians 15:20). “First fruit” in the church age means that those who were saved in the early church were a promise that more would follow. Jesus' resurrection is a promise that we, too, will be resurrected. Any other use of "first fruits" is either abusive or careless.
This presumes that the work of God be understood in a dispensational manner instead of following the teaching of replacement theology. Replacement theology teaches that the church has replaced Israel in God's plan for the world. All of the promises God gave Israel (including material blessings for obedience) are transferred to the church. Dispensational theology claims that God gave Israel and the church different promises, and many of Israel's promises will not come to fruition until the millennial kingdom. Got Questions Ministry believes that dispensational theology best interprets the Scriptures. The church cannot claim all the promises God made to Israel in the Old Testament.
That doesn't mean that giving a first-fruits offering is bad in and of itself. Like the term (or even the practice) "tithing," "first fruit" can be shorthand for "voluntary offering given in thanks or faith." There's nothing wrong with giving above and beyond what is regularly budgeted for—as long as the motivation is personal and not pressured by church leadership.
To say that "laying down a seed" so that God will make someone rich, or that you can pay off God to bless future plans, is an abusive lie from adherents of the prosperity gospel. To give sacrificially is to follow in the example of the widow of Mark 12:41-44 and is commendable as long as it isn't coerced. To give an offering in thanks that God provided is perfectly acceptable. But if a church wants to have a period of fund-raising, it would be better to have a specific purpose and not just try to spiritualize the desire to have more capital in the bank. The New Testament says we are to give in faith, but it doesn't say that we are to give to the point of destitution so that our faith can grow (1 Corinthians 16:2). There is a difference between faithful sacrifice and bad resource management.
God wants all of us (Romans 12:1). Every monetary blessing we have is His, and we should do with it as He leads—whether to use on ourselves or to use for others. Matthew 25:14-30 tells us that we should be responsible with His blessings. This would include giving for a purpose, giving by the leading of the Bible and the Holy Spirit, giving for the spread of the Gospel and the aid of the needy, and giving cheerfully. Whatever you choose to call that, it's simply Christian giving.