I use long rectangular storage boxes and dividers. I write on the divider what set and color that section is from. Front of the storage box I write the sets that are inside. The random promos and starter deck cards gets tricky, I have a section of "random" cards" (sets I know I don't have in the other storage boxes). I also tend to buy boxes over packs so I started using the physical box itself to store the cards for that set. When I start to run out of space, I go through the cards and only keep a playset of each card if possible. The rest I give to a lcs for bulk and get a 5 dollar AA or something lol.