Your options are limited for new shifters for a 3x9 Shimano road setup. If you have Tiagra shifters already, then you have the best of the new ones that are currently available. You might be able to find some used ones that were originally higher quality: 105, Ultegra, or Dura Ace, all of which will be from at least five years ago, but finding used ones of those that are still in good condition might be hard (and finding new old stock will be virtually impossible). Furthermore, although they might be a few grams lighter, I doubt they would function any better than the Tiagra ones you have. There are some ways to use shifters from other manufacturers to operate a 9-speed Shimano rear derailleur, but then you really need to know what you're doing.
If you're shifting is not smooth, then it's most likely to be that it is not adjusted right, and not because your shift levers are not high quality, or due to any other specific part. Even when adjusted right, Tiagra-level components are not going to shift quite as smoothly as higher level components, but to get the smoothness of the higher-level parts then you'll probably need to upgrade everything to higher level components, and not just one or two of the parts. Doing that will probably cost as much as will buying a new bike and selling your current one, which would be the option that I would choose between those two. But, for now, get someone skilled to give it a good service and see how good is the best the current components can be. That person will then hopefully be able to tell you if there is one specific component that is causing a problem with your drivetrain, and in that case that alone should be changed. Your approach seems to be to randomly change parts in the hope that things will improve, which is a bad strategy.