Sketchup is a great program for what it was designed for, 3d conceptualization. But it is not quiet matured to the point of being 100% integrated into the 3D artists workflow.
The problem is that SketchUp's UV mapping is, well, nothing like traditional 3D design software. It is not impossible to make the necessary fixes and tweaks to the exported .obj files but it can be an ever expanding pain in the arse as the model complexity increases.
I would suggest if you are serious about 3D modeling and gaming while on a budget you might consider Blender. It is not perfect but better suited to the task.