Factory trigger setting, 3-9X scope, commercial ammunition that may not be the rifle's favorite...all of these are likely making a contribution to the modest accuracy/precision you're experiencing. Obviously, the easiest thing to do as a starting point is to test different types of commercial ammunition to find one the rifle prefers. All you need is one box each of as many different brands that cover a range of bullets, velocities, etc., as you can afford. Chances are you will find one or two that will be heads/shoulders better than the others.
Optimizing the trigger setting is another thing you can do that might not even cost you a single cent, if you can adjust the current trigger to your liking. Follow the directions, and don't try to push the envelope on how low you can set the pull weight initially, as setting the trigger pull too low can often be a safety concern.
Fixing the low magnification on the scope is likely to be a much more expensive fix. I'd worry about that when you can afford to do so, and not before. In other words, save up, if necessary, to get a quality optic. Don't rush out and buy something you may not be happy with later, simply because it goes up to 25X or 30X, or even higher. Good glass is an investment and will last a very long time...it's worth taking your time and purchasing the right glass for your application(s). You can spend pretty close to however much you want and the following manufacturers are listed in what I would generally consider increasing price: Sightron, Vortex, Nightforce, March. There are plenty of others to choose from as well. Find the best scope that suits your needs, even if it takes a while to get it. I would not recommend "settling" for something in the meantime; that's just more money out of your pocket.
Over the long term, I would consider learning to reload if you don't already. You can certainly try to find a commercial ammunition that the rifle likes, but this is really just a poor man's approach to reloading. Reloading gives you the opportunity to select the bullet you want to use, and then to optimize the load for your specific setup. It usually pays off big in terms of precision/accuracy.