If you use a paterson type plastic reel, then a few tips:
Make sure you cut the leader to where it bends inwards (to the emulsion side), if your camera is one of those that winds it onto the camera spool the wrong way round. The inflexion in the film tip should follow the reel's bend. Sometimes that means having to rewind the film and letting it stand for a day or so until the reverse kink is straightened out.
Do not bevel the leading tips, as that will allow the film to slip out of the groove. It must be perfectly square, with sharp tips if it must. You can bevel the tips later before loading into the sleeves.
Make sure the spool is absolutely dry before loading film. Emulsion will instantly stick to a wet surface, and the spool will be impossible to load.
From the rest of the info you give, it seems you developed an unexposed film. When you cut a bulk film leader after loading into the cassette, use a "normal" leader as a template. If your camera is a manual one, then after loading the film in the camera, use the rewind lever to wind back until you feel that the film is tensed. (If it didn't tense, just be careful of winding it all the way back into the cassette, as it is an annoyance to retrieve.) Then when you wind the next frame, check that the lever turns as you wind - that would indicate a positive uptake. I can offer the consolation that it has happened to most of us, some more than once.
Regards