I have dealt with this topic before, but many players still are confused, so will post anew.
There are a number of different types of items that can be required for the completion of Quests in CityVille. These include the following:
Specific numbers of Crops that must be harvested and/or the Mastery of Specific Crops;
A specific Residence or Business that must be in place either in your City or in a Neighbour's City;
Specific Decorations placed in your City;
Specific Number of Building Materials required to complete a Building or Construction Project that is the subject of a Quest.
Crops generally are unlocked by achieving a specific Level of Experience. Planting a Crop usually will not satisfy any requirements but harvesting Crops are requirements in many Quests. Mastery of a specific Crop can be a requirement in a Quest as well and this is achieved by harvesting a specific number of Crops.
Residences can be obtained in a number of ways. There are Residences that will appear in your Inventory as a reward for completion of a Quest or as a Prize for staying at a Hotel or earning the daily Energy Bonus. Other Residences are unlocked by achieving a specific level of Experience or by completing a Quest. Finally, there are Residences that can be purchased, either with Coins or with CV Cash. Some of these always are available in the Marketplace. Others are limited Editions that are time-restricted. Premium Residences usually allow far greater population increases than Residences that can be purchased with coins. Note that Residences, like Businesses, seldom will be complete when purchased. You need to use a specific amount of your Energy to complete them.
Businesses are similar to Residences in the manners in which they can be obtained. Like Residences, some are rewards for completing a Quest or prizes for having VIP status at a Neighbour's Hotel. Others are purchased in the Marketplace and, like Residences, some are premium purchases and some are time-restricted.
Note that there are items in 'Collections' that can be obtained solely by harvesting from a specific Residence or Business. The completion of Collections can result in the acquisition of a specific decoration, but usually is a reward in the form of Energy or XP. The CD Players required in the first Dance Request is an example of a Collection Item that can be obtained solely by harvesting from two specific Residences.
Decorations take many different forms from pavements to ornamental items and can be obtained in a number of ways. They can Rewards for completion of a Quest or Prizes for obtaining VIP status in a Hotel. They can be obtained from a Mystery Gift sent by a Neighbour. Finally, they can be purchased in the Marketplace in the Build Menu under Decorations and like, other items, can be available all the time or be time-limited special items. Placing a specific Decoration in your City can be a Quest requirement.
Of all the items in CityVille, it is the building materials that can be the most vexing as they often need to be obtained in large quantities in order to complete a Construction Project or Upgrade. It is the methods by which building materials are obtained that confuse some players.
First, it should be stated that most building materials CAN be purchased but the price given is for one item and not for the total number needed. The price always is in premium cash and this avenue can be prohibitively expensive. It is far better to obtain the items from Neighbours.
The methods by which Building Materials can be obtained from Neigbhours are:
First, by generating a request through the building construction project menu by clicking on 'Ask Friends'.
There are two separate methods by which a player can 'Ask Friends' for an item and the GAME determines which of these is to be utilised in any specific case. When one clicks on the option, one either will be given the option to Post to the Player's own Wall or to choose to send individual Requests to Neighbours displayed on a list.
When a Request is posted to a Player's Wall, the game determines how many Neighbours/Friends can click on the request to fill it. Usually, there is a limit to the number of players that can help and this number seldom equals the total number of items needed. For example, a Player may need 14 of a given Material for a building project. When the Request is posted to the Wall, it is possible that only 2 Players can click on it. What this means is that Players often must post the same Wall Request again and again.
An individual Request allows the Player who receives it to send one item to the Player who requested it. If a Player has many Neighbours, He/she often can complete a Material requirement faster for the items that can be requested individually.
There is a big difference between a Request posted on a Player's Wall and one sent individually in terms of its effect on the player who fills the request. Wall Requests usually come with a reward either in the form of the same item that was requested or in coins. The Item Reward is far better than the coin Reward, although once again, it is the game that determines which one will be applied to any building Material request.
Note that a Player who visits his/her Neighbours' Walls therefore can obtain many of the building Materials that will be needed to complete Quests simply by helping Neighbours. This is where the Wall Request is better than the individual request. On the other hand, it involves more labour on the part of the Player who wishes to help.
Other methods of obtaining Building Materials are the Wish List and the Mystery Gift.
Mystery Gifts can be sent to Neighbours and can contain a wide variety of items, including Building Materials, Coins, XP points and Crew Members for Community Buildings. They are found in the Free Gifts Menu and can be sent a couple of times each day to all Neighbours or Facebook Friends. If a Player is patient, he/she often can obtain most of the Building Materials needed for a project simply by accepting Mystery Gifts.
The other method by which Building Materials can be obtained is the Wish List. The Wish List is displayed above a Player's Inventory. He/she can place up to five different items in the Wish List, either by dragging an item from Inventory or by going to a Quest and clicking on the plus sign (+) next to any given Building Material.
Neighbours can find a Player's Wish List by accessing the Neighbour Tab when logged into CityVille. A Neighbour can send all five Items on a Wish List in a matter of seconds provided he/she possesses them. Note that any Item sent will be the Item from inventory and it therefore does not make sense to send Items that a Player will need for his/her own Quests! It is only extra items from completed Quests that should be sent to Neighbours via the Wish List option.