Hmm... in everyday North American English "guys", as in "hey, you guys!", while, perhaps, far from proper, is commonly used to adress mixed company and has no percieved or implied gender exclusivity.
But, back to the subject at hand - I do agree with Ann 100% - moreif it was possible

that you should keep all your negs. How much room can they really take up? And yes, I cannot agree more with Onno. The whole photography song and dance, as well as financial investment, aims towards that little celluloid rectangle (or square). It is the one irreplaceable part - after you pull the roll of film, you can drop your camera in a canyon, burn all your prints, etc., you will still have the magical entity onown as the negative which is the only irreplaceable component. Sure, you can re-take a picture... but will it be exactly the same? My suggestion is go to the website of one of the excellent outlets that sponsor this site and buy in bulk. I know it hurts to throw down a wad of cash for something so trivial, but it will cost you less in the long run, and once purchased, you won't have to spend money again for a long time on one of these items - out of sight, out of mind, and well worth it. Think of it as clothes for your negatives, or a good lock for your front door. Or a fridge for your food. There is so many little culprits just waiting to prey on your unsuspecting negatives, its best to protect them.
And as to those cuts - as long as you dont damage the exposed area, who cares if they are all that straight. It certainly matters less than what you store them in... and you were willing to skimp there
Here is my method:
I have a shelf in a closet that is a bout chest high, one of the modular, cut to size meta-rod types, but any metal rod about that high will work. Hang negative so that you can have it flat in relation to the ground when holding up the free end. Now, get a good pair of long, sharp scissors ( I use hair dressers scissors I "borrowed" from my mom a long time ago). Count the frames that fit your sleeve size and rest space between frames on the bottom part of the opened scissors. Pull slightly on the neg (lightly!) to get it flat against the scissor, and cut with a smooth but decisive motion.
Also, get neg sleeves that fit the roll sizes you most commonly use - I bought some recently that take 35 frames of 35 mm film, in 6 rows of five... Guess what happens - usually, I have one or two frames hat need to go into the nex folder... Oh well, you live, you learn.
Best of luck and sorry about the novel...
Peter.