Another version of the cliff's notes is to buy ETFs instead of index funds. ETFs are more liquid since they trade the same as stocks. As you learn more and accumulate more money, you can also start buying individual stocks.

The top Index ETFs that I would recommend (index in parens):

  SPY (US S&P 500)
  DIA (US DJIA)
  BRK-B (Berkshire Hathaway*)
  EFA (MSCI EAFE, aka developed countries in Europe and Asia)
  EEM (MSCI Emerging Markets, aka China, Korea, Brazil, India, etc)

I would recommend at least 2/3 US indexes and the rest international. Don't worry too much about international exposure since all US multinationals operate globally; e.g. buying Coca Cola (KO) is actually a bet on economic growth in China.

* While BRK-B is not an index ETF, it's actually the first stock I would recommend for new investors to buy. BRK-B is Warren Buffet's company and has broad exposure to the US market.