Preserving and Rejoicing in the Glorious Gospel

The true Gospel is always at risk of dilution or pollution. The council of Jerusalem was the first council of the church organised to deal with error in the church that was capable of threatening the salvation of sinners. The nature of this error was adding to the Gospel and to leave the error unchecked would have caused many to stumble and allowed a false gospel to be received by future generations. So what key points can we learn from the way the council responded to the error?