Get Good Coffee
Why start with good coffee?
The most important part of making good coffee is the quality of the beans/grounds you start with. Every other part of making good coffee (like the grind, the water, the brew method, etc.) is just trying to "bring out" the quality of the beans you started with. You'll never make a cup of coffee that's "better" than the coffee you made it with.
What makes coffee good?
Lots of factors go into the quality of coffee beans—there's a whole industry behind it, actually. For the home coffee game, lots of those factors are of vanishing importance—things like country of origin and growing altitude and roast profile will have minimal effects on the tastiness of your home-brewed cup.
For the home coffee game, the most important factor is age. Get coffee beans as freshly roasted as you possibly can. After that, experiment with different roast categories (Light, Medium, and Dark) to find one that works for you.
Do I have to buy expensive specialty coffee?
Price and tastiness don't correlate 1:1. Old, expensive specialty coffee is probably worse overall than fresh, inexpensive commodity coffee. But with that said, in general specialty sources, especially if they roast local to you, are more likely to be fresh (and more likely to explicitly date every bag, so you know for sure how old the beans are that you're working with). Value freshness over fancy packaging and "authentic" coffee shop vibes. But if you can afford it, and if you have a grinder nice enough to get the advantage from it, fancy specialty coffee is often (but not always) among the best-tasting options available.
Are there any other options to know about?
If you're ready to embark on an entirely new level of coffee-flavored adventure, you can try roasting your own coffee beans! Green (i.e. unroasted) coffee is often much cheaper per pound than roasted coffee, and you can usually get it in bulk for an even better price. I haven't tried roasting coffee myself, so if you're interested in that you'd need to find another source more helpful than this one. 😄