Brewing delicious coffee really only requires these 5 things
Fresh Roasted (within 2 weeks) Specialty grade Coffee
Hot water preferably filtered to remove chlorine but retaining some minerals (no distilled water) at 198 degrees f to 202 degrees f.
A decent coffee grinder capable of grinding the desired particle size with little variation of pieces from that desired size.
A Brewer or devise that allows the hot water to pass through your ground coffee then separate the grounds from the coffee in about 4 minutes.
And, this basic bit of chemistry or physics knowledge:
The larger the particle size of your grounds the less surface area you will have exposed to the hot water and will therefore extract slightly less of the total flavor of the bean.
In terms of taste this generally means large size Course grind will be less bitter but weaker if using the same amount of a finer grind. The important thing to remember here is to use the proper Grind size (within a range) for the brew method you choose. Course Grinds are good for Press Pots (French Press) and should produce a rich round less bitter taste but may require more coffee per cup to reach the strength you like. Pour over through a filter and most standard home brewers work well with a medium grind you will want to experiment by changing the grind slightly one way or the other while using the same coffee and amount of coffee. With filters if you go too fine you will plug the pores in the filter and end up with weak or bitter coffee. If you try too course a grind your coffee will taste weak which can also be bitter because the coffee can't release enough of it's flavor so all your senses detect is the bitterness.
Bitterness is a sign of just plain Bad coffee, Stale coffee, Weak coffee (how much coffee with how much water), Improperly Ground coffee (very small particles in with a medium grind will plug a filter), Poorly brewed coffee (too fast or slow, too hot, left on a burner), and should not be confused with the bitter sweet taste of a Dark Roast coffee.
A good brewer simply delivers the proper temperature water evenly over Freshly ground coffee in 4 minutes.
Excellent and cheap methods of brewing a few cups are the French Press and Pour Over or Dripper, either one is available in Department stores from $3 to $50 on the high end. Ad a good Grinder $129 from our Grinders and Accessories and any method to boil water then pour just after boil stops.
Below Bodum French Press empty with plunger all the way down. About $20 - $50 depending on size.
Hario V60 Dripper (Pour Over) with filter and an "I Roasted This Coffee Mug". Plastic Drippers are available under $10, Hario Ceramics about $20 - $30.
Baratza Encore Coffee grinder with French Press
Medium Ground Fresh Coffee into Hario Dripper
Nesco Hot water Kettle pouring just below boiling water onto grounds in Pour Over Dripper, stay around middle pour slowly but under 4 minutes.
This is really good coffee!