Choose a carpet that is a "100%" blend.
Mixed fibres are generally to make carpet cheaper. The main fibre types are Nylon, Polyester, Polypropylene, Wool, Triexta.
Carpet is made in many different styles, the main types are cut pile and loop pile.
Loop pile's won't show shading, however tend to show the joins more.
All cut pile carpets will show some signs of "shading" or "tracking", where you can see your footprints on the carpet. The best way to minimise this, is to choose a carpet with a dense pile, where the fibers are packed tightly together. A shorter denser pile won’t track as much as a longer looser pile.
Having a quality underlay is very important and should not be overlooked.
Underlay is measured in both thickness (9mm to 12mm), and density (90kg/m3 to 130kg/m3)
90kg would be the bare minimum to use and 110-130 kg would be the best ideal weight to use.
A good dense underlay acts as floor insulation.