By 'high-tier' and 'low-tier' I'm merely referring to the number of details a single C4D has. For instance:
High-tier: http://www.renders-graphiques.fr/image/upload/normal/C4D_3-1.png
Low-tier: http://imagenpng.com/wp-content/uploads/2015/03/renders-c4d-6.png
In the first one, the possibilities when rotating, scaling up and down, squeezing and re-coloring the C4D are much higher compared to the second one. A good C4D is that that can add details to your background, not just fill it with something.
It comes with practice anyways, keep experimenting with different C4Ds with each tag you'll get the idea. Also, I'm the only one who refers to them in 'high/low-tier', it's my own way of describing C4Ds. You could just call them high-detail C4Ds or low-detail C4Ds.