How are + Action cards used in Dominion?
When playing a +Action card do not resolve the extra action until the current card is finished.  From pg. 7 of the rules


  It does not mean play another Action immediately. The
  instructions on the current Action card must be completed before playing
  any additional Actions.


You should total up all the extra coins on the cards you've played for one purchase unless you have played cards with + Buys.  (You don't have to spend everything you've gained in each turn BTW). (also page 7, under Buy Phase)


  The player may play
  some or all of the Treasure cards from his hand to his play area
  and add to their value the coins provided by Action cards played
  this turn.