If I'm supposed to do this, then why did the following take place?
Returning to Acts 15, after much debate and discussion, Peter says that "[God] made no distinction between us [Jews] and them [Gentiles], but cleansed their hearts by faith." (Acts 15:9 KJV), and James the Just (the brother of Jesus) states that "we should not trouble those of the Gentiles who are turning to God" (Acts 15:19 KJV). They sent a letter accompanied by some leaders from the Jerusalem church back with Paul and his party to confirm that the Gentile believers should not be overburdened by Mosaic Law beyond abstaining from food sacrificed to idols, from blood, from the meat of strangled animals, and from sexual immorality. (Acts 15:29). The letter also refers to Barnabas and Paul as "beloved" (Acts 15:25 KJV); compare Paul's account "James, Cephas [Peter] and John, those reputed to be pillars, gave to me and Barnabas the right hand of fellowship" (Gal. 2:9 KJV).
However, note that Sha'ul denied teaching people to stop obeying the Torah, and was in fact perfectly willing to take a Nazrite oath and perform the attendant sacrifices involved to prove that! Therefore, teaching that any Apostle believed that the Torah was done away with by the coming of the Messiah is false, especially since Yeshua Himself said that not the least letter or penstroke of the Torah would pass away until Heaven and earth did, and that those teaching others to disobey the least commandment would be the least in the Kingdom of Heaven (Mat. 5:17-19)!
Note further that in Ya'akov's judgement in the Council, he finishes by saying, "For Moses from ages past has those in every city proclaiming him, being read in the synagogues every sabbath day" (Acts 15:21). Look at what they required for fellowship: "They should abstain from pollutions of idols, and from fornication, and from things strangled, and from blood" (v. 20). Notice that loving one's neighbor, not stealing, honoring one's parents, and a host of other commands which we would consider as still binding are nowhere there--neither is baptism or the Lord's Supper, for that matter! Are we then to assume that they regarded these commands as the totality of the Torah that Gentiles should follow? Not at all!
Rather, each of these four items seems designed to separate a new believer from their former pagan practices: Idolatry needs no explanation. Fornication was typically done with temple prostitutes. Drinking blood and eating meat sacrificed to idols were also typical practices. Therefore, the minimum requirement for fellowship is that the new believer completely give up all other gods and their worship to worship the true God, the God of Abraham, Isaac, and Jacob, alone.
Having done so, they would be considered "clean" enough to enter the synagogues as "God-fearers" and learn about all the Scriptures, including the Torah. From there, the Apostles trusted the Holy Spirit to continue what He had started in their lives.
But the core issue is that the Gentiles who had received the Spirit by faith were already saved, and were learning to walk with God rather than needing to be saved by walking with God in just such-and-such a way. The RCC faces a similar reversal of cause-and-effect when it teaches that baptism is a prerequisite for salvation instead of an act of obedience that comes willingly as a sign of salvation.