We humans are selfish by nature. Generosity is not something that comes naturally but is the result of God's grace in our lives. This is why Paul refers to the Corinthian offering as this act of grace (v. 6).
Charis is used both here and in the next verse of a spiritual endowment or gift of the Spirit. The Corinthians take great pride in their spiritual endowments. And well they should, since they do not lack a single one of them (1 Cor 1:7). Not only this but they excel in them--or at least in faith, . . . speech, . . . knowledge, . . . earnestness and love (2 Cor 8:7). Paul consequently pushes them to excel in giving as well (see that you also excel in this grace). Giving is identified as a gift of the Spirit in Romans 12:8, where Paul exhorts the Roman believers that if one's gift is contributing to the needs of others (metadidous), then that person should give generously (en haploteti; compare 2 Cor 8:2).
All things considered, the list of endowments here is a modest one. The first three are gifts of the Spirit. Faith is grouped with gifts of healing and miraculous powers in 1 Corinthians 12:9-10. So Paul is probably thinking not of intellectual assent to a set of propositions but of a belief that God can and will act in a particular situation. This kind of faith, Paul says, is able to "move mountains" (1 Cor 13:2). Speech and knowledge are too areas of gifting that Paul refers to in 1 Corinthians (1 Cor 1:5). Speech may be a catchall term for such oral gifts as prophecy, teaching and tongues (1 Cor 12:10, 28). Similarly, knowledge may refer to the gifts of discernment, word of wisdom, word of knowledge and interpretation of tongues (1 Cor 12:8, 10).
Also among the things that the Corinthians excel at are earnestness and love. Spoudh denotes the earnest engagement or zealous pursuit of something. Paul has already made reference to the Corinthians' earnestness in trying to clear themselves of any and all blame regarding his public humiliation during his last visit (7:11-12). Love must accompany the exercise of the other four, otherwise nothing of lasting importance can come of them (1 Cor 13:1-3).