My 2 cents
Purge model - Everything you do in sketchup adds to the file size even if you delete it - the only way to properly delete it is to 'purge model'
window >model info > statistics > purge unused
If you have a video card that does not support OpenGL then you disable OpenGL
Preferences > OpenGL - untick 'use hardware acceleration' and 'use fast feedback'
even if you have a full OpenGL video card it works better to disable them
And of course turn off 'autosave' also