Most people tend to run Cat 5/6 in pairs. It’s pretty cheap and it gives you some built in redundancy. As you are normally pulling it out of 305m boxes, you just pull 2 boxes at a time. However much Cat5/6 you put in, it will never be enough, trust me. For Cameras I use cat 5e as it is more flexible and easier to terminate into cameras. Think about everywhere that you may want a camera and cable it now. e.g. if you have a side gate, think about one covering it, driveway, front door, back door, patio doors, shed, back garden etc. Maybe not all, but once you have cameras, you will want more.