Welcome to the forum & to collecting. A great bunch of folks.
First I’d decide what information about the cartridge you might need to reference when your away from your collection & need to see if you have it. This might just be the headstamp, bullet, case material & primer. Or if you just intend to collect one of each case type, just the case type, which is simple. But you’ll start seeing different headstamps or bullets & want to add those. So, my 2¢ use either a computer or a note book, which ever is handy for you, & record the important information with as much detail as you can. I wouldn’t get into measurements as variations in manufacturing can then enter & drive you crazy. I use abbreviations & keep a record of those so you can maintain continuity throughout your ‘book’. br=brass, cu=copper. pi=primer ca=case I start wit the headstamp & then primer, crimps, case, (including pertaint details cannelures, mouth crimps, or shot size, hull color, over shot card colors & print if you collect shotshells) bullet shape, material & magnetic or cored & that sort of detail. Group photos might well work, (make sure thay are high quality) but as you add new you need to update. In this digital age that is easy & cheap.
I just number in order that I get them & then enter the case type in another book under the case type number I can add the numbers for future cartridges of the case type. (ie my 1st .303 might be number 45 & so any future 303’s might be 79, 206-225, 409-410 & etc.).
I’d also include the price you paid so should you come across an extra you have an idea of worth in trading it. And (God forbid) in case of loss it gives you proof for insurance or value for a police report.
All this said look at what you think might be the way you will need to use this & structure it so you can easily use it. Remember the simpler the easier. but as you know with cartridge collecting the details are very important.
You guys have lots of shows, go to the next one & poll the members about how they keep records. & how they use them.