Im have been Poser for about three months now and still have no clue whatsoever how to create custom figures. I am also a tad clueless about how to properly create textures. If anyone can hint me to the right path, I would be very greatful. Thank you.

Depends on what you mean by custom figures. Creating new object files, morphing existing object files, just applying texture to existing characters? As for textures, get the templates for what you want to create a texture for, take it to Photoshop or Paint Shop Pro, make it the base layer, then paint your texture on another layer. When you are done hid the base layer and save it. And you now have a texture you can apply in the material room. Go to the top of this page and above and to the right of Forums you will see Tutorials. Click on that and start reading those.

How to create custom figures?
Step 1: create the mesh (OBJ-File). No ordinary human being can do this within Poser itself, so you need a modeller.
Step 2: import the OBJ into Poser, goto the setup room and set up a skeleton to it.
Step 3: Group the polygons to the belonging bones.
Step 3a: adjust the joints.
Step 4: create a texture.

And this is the reason why most figures cost money because: if you do this all by yourself it takes months. (Except if you make something lik Dr. Geep's Boxman. But this is a very good practise for beginners.)