How to export a fbx file from Blender to Unity with material included:
Unity 2018.3.2f1 Personal
Notes: I'm using Blender version 2.79 and Unity 2018.3.2f1 Personal. If you are using any other version please keep this in mind that this instruction might not work ;)
In this instruction, I will only use a simple cube as an example, but you can use this instruction for any model.
1. Open Blender, before you export your model as a fbx file you should delete the Sun and Camera because you already have the Sun and Camera in Unity. When you import from Blender to Unity without deleting the sun and camera, it will have 2 cameras and suns and it will confuse Unity as to which camera and sun it should use, so delete those before exporting.
-Click on the object that you want to delete.
-To delete tap X, then delete.
2. Check if your model looks normal. In a normal model, the faces of your model should be facing outwards. If the face's direction is pointing inwards then it needs to flip to normal. This example shows a model that is not normal then it flips the model to normal.
-Check if the faces are normal.
-Select the model, tap TAB to go into the Edit Mode (make sure all faces also selected in the edit mode).
-Tap W then it will show an option menu, then click on Flip Normals.
3. Add a default material to your current model.
-Select your model, then on the right side of your screen, click on Material (a circle with black and pink).
-Tap TAB to go into the Edit Mode (make sure all faces also selected in the edit mode).
-On the right side of your screen, you can change the material name to whatever name you want it.
-Then click Assign, and go back to Object Mode by tapping TAB.
5. Export as a fbx file to Unity and test material.
-Click on File, then Save.
-Click on File, then Export as a FBX (.fbx) file. Choose where you want to put your file.
-Open Unity, then drag your FBX file under Project Assets in Unity.
-In Assets, check if your model is there. Then drag your model to your Scene.
-Finally, add whatever material you want into your model.
4. UV mapping the model.
-Go to the bottom left side of your screen and drag out another editor.
-Tap T to remove the toolbar on the left side (you don't need to remove it if you want).
-On the left editor screen, change Editor Type to UV/Image Editor.
-Go back to your model, and tap TAB to go into Edit Mode (make sure all faces also selected in the edit mode).
-Tap U to have UV Mapping option, then select Smart UV Project. Then click OK.
-On the left side, the UV/Image Editor will pop up all the faces that are wrapped.