Mm, I am working with Sketchup too but not for games. Sketchup is not optimised for games I think, because instead of making polygons it represents the models as surfaces. For exemple Unity doesnt reads the surfaces as good as polygon models, I doubt that Leadwerks do. Also you will have a hard time in texturing and making materials for models you create in Sketchup, because Sketchup doesnt creates an UV map. I tried to texture in Mudbox for exemple, but without an UV map of the model, either you will get lots of color artifacts either you can not paint at all. Also keep in mind that if you want to sculpt something you make from Sketchup, you will have an issue because Sketchup doesnt add subdivisions on the model.
I would suggest to switch to Blender which is free and its used by lots of indie developers, plus there are thousands of tutorials.
If you want to invest, you can pick Maya or 3Ds max