First coin: Likely the Lydian Lion, ca. 600 BC in Lydia, Asia Minor (current-day Turkey)
Ideas about money originated in Mesopotamia and the Greek colonies in Asia Minor, through which ideas about coinage and much else spread
Numismatics: is the study of coins and currency.
Word origin: French numismatique, from Late Latin numisma, numismat-, coin, variant of Latin nomisma, from Greek, custom, current coin, from nomizein, to have in use, from nomos, custom. See nem- in Indo-European Roots.
Grading coins: coins get graded according to their technical wear, spots, stains, scratches and dings, eye appeal, provenance, rarety, conditions of manufacture, metal content
There are a number of professional grading services available. Here is a valuable link to coin grading
The same coin may get graded differently by the same grading service, that is, be aware that there will be some non objectivity, hence variation, in coin grading.
Know your source when buying a coin, fraud on ebay is common. Don't buy rare coins there and don't buy into the “gold coin find”. For beginners and with a bit of patience and looking, you can find a nice ancient coin for $10-20.
Exposure to the air oxidizes metal, changing its color. It is advisable, if you are storing your coins for a long period of time, you store them in a controlled environment.
A relatively constant, moderate temperature and low humidity are preferable for long term storage of numismatic collectibles. Placing packets of silica gel in coin storage areas helps control atmospheric moisture.
The more a coin gets handled, the more it degrades.
"Slabs" are sonically sealed hard plastic holders for individual coins. They are best for more valuable coins.
Mylar-line cardboard, often called "2x2s" but also available in other sizes, is a good choice for safekeeping a more average coin.
For interesting US coin trivia, check out: US coin trivia
Get informed, be patient and enjoy your coins, ancient or new.