Get Something Good and Get To Work
"Who knows the secret I don't know, and who is it?" states Barry Schwartz on the TED Radio Hour Podcast 5/4/12 (NPR). When it comes to equipment, buy what most of the people you respect recommend (gear that has stood the test of time) and get to work.
Here's what I recommend...
Harmonica: Hohner Crossover
Microphone: JT30 body, a Shure CM or CR element, screw-on output connector, cable and backup screw-on to 1/4" female adapter
Small Amp: Fender Super Champ X2
Large Amp: Fender Bassman (Early 90's, the one one with the blue-frame Eminence speakers) 5U4 rectifier tube and (right to left from back of amp) 12AY7, 12AT7, 12AU7 preamp tubes. If you like delay, the Dan Electro Dan Echo or Lone Wolf Delay.
There are many other fine products (I love my MegaTone ME18 and Filisko guild custom harmonicas), but for price, availability and versatility, this is a solid list.