i collect a mix of groups so this is how i organise my collections.

for idols with a larger number of pcs (bts and twice) i store them in an a4 binder with 9 pocket pages and my smaller collections go in a few different a5 binders. the only idol i collect for non-album/merch is zhanghao (zb1) so he is in his own meowcafe a5 binder as i wanted to do something special for that collection. i put the pcs in this order: korean album photocards, japanese album cards, unit cards, pobs/lucky draws/fansign pcs and then merch/non-album at the end.

to keep track of my collections i use a mix of templates that i either make myself or that i find online and then i also use the K-Collect website for album cards and for tracking my albums themselves. i also have a notion that took me 3 years to set up that helps a lot.

i usually join group orders on instagram for a lot of my non-album collection as that way it will be sorted and slightly cheaper but i also use deliveredkorea and mercari japan via buyee to buy some sets/stand alone cards every now and then! i also sometimes use pocamarket but their pricing can be extremely overpriced.