Re: can a better pedal improve my technique?
If you can afford a good pedal, get one. A better design, with newer parts and smooth action, will make it easier to play what you can already play.
However, you won't get quick doubles until you practice them in a variety of contexts, and a host of other exercises, every day and for a decent period of time. Maybe the reason you're not making the sort of progress you wish is because you don't know what, and how, to practice? The right methods and materials will grow your skill much faster than any pedal.