The Lord's Supper was instituted among Jesus' committed disciples, and the early church's pattern in Acts shows new believers being baptized and then continuing steadfastly in the apostles' teaching, fellowship, and the breaking of bread. Baptism marks a person's public entrance into the family of faith, while communion renews and celebrates that same covenant relationship together as a community. Someone still exploring faith is warmly welcome to attend and observe, but taking communion works best as a next step after baptism, not before it, so both symbols keep their full meaning.
Salvation is entirely by grace through faith in Christ. His atoning sacrifice, heavenly ministry, and intercession are the foundation of assurance; obedience, Sabbath faithfulness, and loving service are the fruit of a redeemed life, never a way to purchase acceptance with God.