Well, that's what I am talking about. It might be better (to try to learn to master SU) if you tried to join a modeling community that makes models for a virtual reality game.
For example, I was part of a group for an online virtual reality game called IMVU. You not only had to learn how to use SU, but also run as economically as possible. While we weren't encouraged to make the smallest models as possible, as a modeler, means I was also a user (which you couldn't be a modeler until after a year as a user). The FIRST thing you notice about some people's models, as a user, is how slow your game gets when they use big textures and big models (MB wise (which reflects how many polys were used)), so the modeler's success and failure is based on how successful they were at being economical on polys (triangles in model) and size of textures. Because people avoided buying your models if they were too big and slowed down their user experience.
I can tell you our texture sizes were 64, 128, and 256 pixels in size, you could go to 512, but then you had to go 512x256 maximum (You couldn't do 512x512. Any other combination was fine).
The crux of the issue is that user's didn't want to buy models that looked too simplistic either. So, the best modelers were the ones who knew the sweet spot between the two extremes; too simple or too slow. In the community I belonged to in IMVU, the sweet spot was no larger than 2MB for textures and polys in-model and nothing larger than 12,000 polys (the smallest value for the sweet spot was too nebulous to define).
BTW, IMVU sort of doesn't encourage the use of SU anymore as a model-making program. The only way to convert SU models to a file format that the game CAN use was by using a hacker program (which should set off alarms in your head and is partly the reason why I left). My understanding is that Second Life still allows SU models... Maybe there is another virtual reality program out there by now?
That is, of course, just a suggestion as one way of "mastering SU".
I'm aware of game poly size (since I'm a game developer myself). My workflow usually using Collada and FBX format. I have different way of modeling for game prop. Since this car for Challenge I don't limit my self with poly. Online Modeling Community for virtual reality game seams a good idea maybe I should join one.