I went through this tutorial: tutorial link and found out how to make a realistic looking eyeball, which I did:
The images I used to make this was all given to me through this tutorial in the description and if you are thinking of going through this tutorial as well, my suggestion is to reduce the video play speed to either 0.5x or 0.25x, because the guy in the video goes way to fast. The tutorial is also not suitable for beginners.
The first part of the tutorial is the making of the shape, first the eyeball itself, then the iris, a shadow for the eyeball is added in later, but not at this stage. I was able to create the Mesh for the eyeball, but the Mesh for the iris was a bit tricky and I was stuck at this stage for about 20 minutes.
After the shape of the eyeball was done, then came the lighting and that was done in a very peculiar way to me, but was definitely worth the effort put into it.
Once the lighting was done, then came the texturing. The first step was to mark and unwrap the whole eyeball and then open up one of the images given and locate the areas of the eyeball texture to the correct positions, height and rotations. Then finally applying the textures though the texture panel on the property menu on the right.
After this I applied the node setup what was displayed to the Iris and eyeball. This improved the quality of the eyeball tremendously and made me realise even more how important the Node Editor tool is.
The final step of the tutorial was making small adjustments, like pupil size slider and I think adding in the shadow for the eyeball itself. Through this part I learned about shape keys an how important they can be. Shape keys let you record a shape before and after adjustments and use a slider to find the perfect ratio for that object or something along those lines.