Whenever we talk about the gospel, it is helpful and important to remember the four essentials: God, man, Christ, response.
There are four slides (link to first slide) explaining these essentials. They are followed by two slides showing four "hills to die on": the virgin birth, deity of Christ, substitutionary atonement, and physical resurrection.
[These] historic fundamentals represent a few of the more important theological underpinnings of the gospel, and therefore of evangelicalism. So if you find yourself or someone else denying one of these tenets, the Biblical gospel has been compromised and the bounds of evangelicalism have been overstepped.