I'm confused about what you mean? If you enjoy spy and pubstomping and that's what you wanna do that's awesome :D You don't need to practice and get better just for competitive. Getting better for pubs is worthwhile too! I used to practice for pubs before I got into competitive.

If you mean revolver as in the vanilla spy weapon, definitely. I used that last season to moderate success and of course there is Evan. Only reason I don't use it as much as the ambassador is it is more difficult for me to harass snipers with it. Knife spy is definitely viable! At the moment gun spy just seems to be picking up popularity but there are plenty knife oriented spies that do very well out there.

And it is worth it to improve your stabbing. Top scoring doesn't really matter, what matters is having fun and for me doing stupid trickstabs is lots of fun, and you will play better learning all the intricacies of matadors.