While someone can glean the basic concepts of Christianity alone with their bible and the Holy Spirit, basic is about as far as that will take you.
Most folks cannot go to a Bible college or seminary, but that need not limit ones theological education.
There are excellent resources online that are not only comprehensive, but free of cost.
I’m going to note some that I have found very helpful.
This really is a wonderful resource. It starts you at a beginning level of classes and moves you all the way through a biblical education to a trained pastoral level. I simply cannot recommend this site highly enough for those seeking a deeper and more well rounded, directed, Christian education.
These are the same seminary classes taught on the various campuses of Reformed Theological Seminary. From systematic theology to biblical theology to church history, you can learn from some of the most respected set of professors in the country.
Again, on iTunes, full seminary classes on everything from church history to apologetics. The esteemed Carl Trueman teaches here.
A broad range of seminary classes…the church history classes from Dr. David Calhoun are priceless.
A selection of foundational classes.
The original intent of this site was to provide education for missionaries overseas who couldn’t attend Bible college or seminary. It has expanded and one could spend the next twenty years learning from some of the best biblical scholars on the planet, all free of charge. There are audio and video classes available as well as scholarly articles on a multitude of topics.
Any of these sites will move you to a greater understanding of God and His word…all that is required of you is a desire to learn and time.