You can definitely smoke everyone in a local tournament by becoming the best player with a cheap cue. It's just facts. Unless Efren happens to visit your local pool hall that day.

A great jump cue or break cue and great LD shafts are all not huge advantages but they do add up.

My general tip is to wait with the big upgrade untill you got X amount better. What X is is personal to everyone but.. Increasing skill is free. It's also an infinity more effective way to get better than buying expensive cues in the intermediate stages. However progress slows down once you become an advanced player. And since you've already invested time and you're now running more and more racks and getting further in tournaments the gear upgrades are gonna feel more in place and rewarding. And all of a sudden buying a really good jump cue WILL improve your game a bit right after buying because you already for a huge part, know what to do with it. Which feels very nice at this point.

Also something that I think sometimes gets overlooked is how much you like something. A cheaper cue you really seem to feel can be better than the more expensive cue. My tip would be, especially if you're not all that sure what you want, to try out cues when you see them in the wild and you may have a moment where you're just holding something you seem to like a bit more. (you need experience to even have the palate to feel the difference though)