Previous: Find a Brew Method that You Like
Depending on your brew method of choice, making good coffee at home costs around $120-150 to get started (~$50 for a quality hand grinder, ~$50 for brewing equipment, ~$20 for misc. odds and ends—plus, of course, the coffee itself).
Aside from the coffee itself, the number one place to spend is your grinder. Funnily enough, actually brewing the coffee is the easy part—as long as you're getting the water hot enough, there's really not much that a more expensive brewer will do for you that a cheap one doesn't (unless you're into espresso—but that's a whole different topic!).
But improving the quality of your grind has all sorts of benefits:
Aside from that, spend money on conveniences. Pick up an electric grinder rather than a hand mill. Or get an electric grinder that runs more quietly than your current one. Get an electric kettle with a better pouring spout if making great pour-over is your goal. Or get one that heats up faster, if your current kettle is lower-powered and takes several minutes to get hot.
If you want to be really nerdy and scientific about your coffee, you can look into refractometers to help objectively measure your finished cup. But those can cost hundreds of dollars all on their own. So maybe only check those out if you're trying to be a true professional.
Next: Drink Your Coffee Black