What equipment is needed to be able to listen to one of many different bands which are used

Personally i done a lot of research into buying a radio scanner as some scanners can listen to more frequency's  then others. 
All mobile scanners come with an antenna,however i decided into looking in to a mobile antenna for my handheld scanner which allows me better reception.
I allowed my self one hundred pounds to purchase some scanning hardware as well as an air band scanner frequency manual.
i decided to purchase an Uniden Radio Scanner and well as a mag mount antenna.