Virtual gifts are not free, they cost a dollar each to send. However, you can add a little message to them and this will end up on the recipient's friends news feeds. So, in a way you are paying to advertise your product. Virtual gifts should resonate with the recipients' identity to promote a sense of personal affirmation and to get them to appreciate the gift.
The wall is an area of each person's profile where messages can be posted by other people who are visiting the profile. You can put any message you want on the wall and it will be public. You can use this to research the market trends of people's interests and you can also post some message about things that might interest specific people in your circle of friends. Be aware that if you spam the wall consistently with sales ads, you will probably be blocked, and if the staff of social media sites is alerted you could end up being taken from social media sites.
An interesting way to use the power of the wall, is to look for people in your circle who have a high number of page views on their profile. These would be people who have a lot of friends or send a lot of activity to the news feeds. That's the only way to tell what type of page views they might be getting. Then, target these people for your comments on their wall in a way that pulls the people viewing back to your profile.
Finally, Social Ads are a paid avenue for advertising on social media sites. The nice thing about Social Ads is that you can target a specific demographic within many social media sites, unlike Google AdWords. You can target it by different categories: age, gender, interests, locations, and more. You can set up a campaign in either the CPC or the CPM model and choose your budget. In the CPC you are purchasing advertising based on clicks and the CPM model is for impressions.
Social ads appear in news feeds and to the left of the many social media sites profiles and can be paired with a friend's action. So, not only will you see that your friend took some action on your website, but you will also have an ad served in the news feed as well.
Social Ads come with its own metric measuring feature called Insights. It gives you an idea of how well your ads are working and what you might change for another campaign. It will tell you who has engaged your ads and who has not providing some market research directly from the ad you choose to place.