I've been dragging my feet on getting my collection into actual proper storage, and my negatives are currently sitting in an archive box divided up with little folders of acid free paper. I only recently got back into film, which I hadn't shot on since I was a teenager, so my collection is still small enough that I could easily square it away into something more suitable in less than an hour, so it hasn't been a huge priority for me.
I'm still debating what the 'final' sorting and storage method will be, as I'm really not a fan of the idea of things like plastic sleeves that I end up having to drag a set of frames out of. I kind of prefer the little folders in a way as I can open them, get a fingernail under the edge of the negative, and then lift away from the paper without rubbing the negative along them. Of course the downsides are that I wouldn't want to move the collection in them for fear of random scratches from the paper as nothing is very securely held in place, and they don't do much to protect against stray dust getting in whenever the lid is opened.
However, one thing that I have been trying to keep on top of is getting reference scans done so that I can keep a digital catalogue of everything on hand. Physical collection storage becomes based on reference to it from the computer. Everything gets suitable keywords, gets a few notes, and also points back to physical journals/sketchbooks where I've been mulling over ideas of how I want to try making real prints of a given negative when I can get a proper darkroom setup.
This way when the collection grows and I get more than a few dozen rolls of film to deal with then it will still be easy to go back and find an original when needed. Or go back and explore specific elements of the collection by pulling stuff up based on keyword. A friend wants prints of horses for their office? Well, keyword search for horses, skim through what I've actually photographed that contains a horse, select potential targets, and then go revisit the negatives on a light table and decide where to go from there.
Eventually I'll code up a checkin/out system for the physical negatives to make sure stuff is harder to get out of sync.