The age old way of gaining Christian knowledge, has and still is by studying God's word systematically. And that
is probably the best cornerstone of such study even now.
However, we have an excellent adjunct to these studies, with the internet. There are some excellent Bible teacher
available, of course..along with some poor examples.
One I can confidently recommend is Mike Winger. Here, Mike Winger discusses the "progressive' church movement. He of course, does it from a Biblical standpoint.
https://www.youtube.com/watch?v=nYuWlxnqa4o Then there is Justin Peters, who despite his "born with" handicaps, does a fine job of of exegeting the
scriptures. This despite his being a Calvinist
https://www.youtube.com/watch?v=-jvuhOa9wY4