What is the best time to run FB ad to get more audience in less money ?

[Jake]

Time is probably a relatively small factor, compared to rich variety of demographic targeting settings in facebook ads. Most people don't worry about timing and run 24 hrs a day, some try to avoid drunk clickers and don;t run ads very late at night, particularly of B to B ads.

If you are getting a decent CTR, click costs will tend to drop after running the ad for a while, limiting it to $2 a day is going to slow the testing process. Image selection is one of the biggest factors in Facebook ads, Always try a number of different images, keeping only those with the highest ctr.