I'll offer some voxel model advice since a question was asked about advice for newbies.
I have never been good at polygon models, so I make voxel models. Two of the most popular voxel modeling programs online are Qubicle Constructor and MagicaVoxel. The latter is the one I use more because of its ease of use and free download. Both can export models into the OBJ format, but you need to buy Qubicle to have that functionality for that program. Qubicle is used by lots of people, especially game developers. Games like Crossy Roads, Qube Space, Discoverie, Stonehearth, and many other commercial independent/indie type games have been made with Qubicle. The reason I why I use MagicaVoxel is because it is easy to make a model using a set palette. Models in MagicaVoxel are limited to 126 (126 pixels long, 126 pixels wide, and 126 pixels high) pixels. So larger models will have to be broken up. MagicaVoxel is less buggy than Qubicle, and it doesn't take too much to make decent models. The biggest thing MagicaVoxel lacks is some way to break up individual models- which is key for if you want to animate models in the future. So you may have to edit the models in another program.
Besides Qubicle and MagicaVoxel, two other programs are popular for making voxel models- the in-progress VoxelShop and Zoxel. I am not as experienced with either program, but I think both are free voxel editors. VoxelShop allows you to break up voxel models into individual layers. The biggest reason why most people use VoxelShop is to export voxel models into the Collada (DAE) format- a format key to use in Unity 3D. I am terribly inexperienced with Zoxel, but all I know is that it is a free program for making voxels you can animate.
So there is your voxel insight from me. Look up each of the programs online and have fun making voxel models! Check out some of my past posts in this thread to see my own voxel art that I made.