Facebook will now gather more personalised information about you and serve you Ads that are specifically on subjects that interest you.

You can learn the answer partly by looking at your Google Analytics account where it will show the percentage only searching on a mobile.

Bounce rate is a very important figure in helping you decide what your website visitors like and dislike.
When you know this information you can start to make decisions on what to change to improve the user experience and ultimately your leads & sales.

This is a great question of which you will get different answers depending on who you talk to.

We believe if your budget is tight then there is no question you should always go for a mobile site (Preferably customised as well as responsive) as assuming you already have a significant amount of website visitors you have a great chance of converting more of them into sales and leads.