I think the easiest point of entry into having a great cup of coffee is to go buy some good beans already ground and get a simple/cheap French press. You will immediately taste the difference from your Keurig swill. Hot water, good coffee and a slow extraction make magic!
Soon enough you will graduate to wanting a nice grinder to chop up your nice whole-beans so you can have a truly fresh cuppa.
Personally, I’ve run the gamut of expensive espresso machines to pour-over and everything in between. I start every day with a fresh grind of dark roast beans into a large French press caraffe that yields 2-3 cups of goodness and I don’t think more strenuous methods are worth the effort by comparison.