ZBrushCentral

I am new to 3D modeling

I am brand new to to 3D modeling. My friend has been doing it for years now and he suggested zbrush to me since that is what he uses. I have noticed that most people on the threads and most of the videos in zclassroom are for people that have some experience already or so it seems. I have watched all of the vids on classroom and have played around with the program for a good while now. But I am still lost in it at the same time. I am trying to create mesh products for an online multiplayer game where the community will by my products from a market where products are posted. The game only allows lower poly mesh models (usually around 12k poly or less). I can link them if they are too big to fit the 12k after they are in world but i still have to keep in mind how much memory they take up. They game i create for is Second Life by the way. I have made a good amount of money creating with their in world primatives so far but if i learn to make the mesh that has just recently been accepted to upload by users then i stand to make a considerable amount more. But, being new to all of this is tough for me to even make basic shapes on zbrush. So all of this being said (I tried to give as much info as possible to make it easier for those who are willing to assist me) I would really appreciate some advice or help on how to further my learning being what I am ( a newbie :\ ). Thank you all. - Johnny