We were confused by the + action cards. It says you have to start at the top of the card and work your way down. so when do you play a second action card and are you allowed to play another action card if you havent done everything on the first action card. Also, can you total up all of the extra coins on all of your action cards and combine them for one buy?
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.
You should think of actions, coins and buys as value stores that you add to and subtract from throughout your turn by doing certain things. So, you start your turn with the ability to play 1 action and perform 1 buy. Playing Village costs you 1 action (bringing you down to 0), but adds 2 back, meaning you now have 2 actions available. Playing Smithy costs an action, bringing you down to 1, and you could still afford to play another card. But Village increments the value so you can play the actions after you finish playing the Village, as opposed to being forced to play them immediately. Similarly, buying a card costs a buy and a specific number of coins. If you've played actions that gave you +1 buy and +5 coins in total, and you have a Silver, you can afford to buy up to 2 cards worth up to 7 coins.
+ Actions add to your action total, but you do not play actions immediately.
Having said that, there are 3 cards that do cause immediate other actions:
Golem forces you to play the other two action cards you turn up immediately, but you choose the order.
Throne Room causes you to play another action from your hand twice. King's Court causes you to play another action from your hand three times.
There are also 2 cards that play coin cards immediately:
You don't have a choice whether or not to play the next coin card you turn up. As soon as you play Venture, the top coin from your deck will be played, even if it is a Loan, Contraband, or Bank that you'd rather save until later.
A promo card. When you play Black Market, you can choose to play some or all of the coin cards in your hand.
Here's an answer to your second question: Yes, you should total all the coins on your (action) cards and combine them for your buy or buys. (Note that you resolve buys after resolving actions.)