Simple is not bad . A lot of photographers like to keep a UV or 1A filter on their lens to protect the front element. I keep a 1a on the lenses I use when hiking around for wildlife etc. I usually keep the lens cap on too, but have lost a few of them, so I have both until I am ready to shoot. Sometimes I remove the filter hoping for a little better sharpness or something.

A circular polarizer is a must in my kit. I have 3 sizes, 55mm, 62mm and 86mm. Most of my minolta lenses are 55mm diameter. Some are 49mm. A set of filter reduction adapter rings allows me to use those sizes on all my lenses, and my wife's canon lenses too.

Thea is about as simple as it gets.

Phil