You're product is either needed or wanted. It's much easier to sell stuff that is wanted rather than needed. If you can figure out how to turn something that is needed and appeal to the emotional want side of a purchaser you will have an edge.

When you go to FB your simply duplicating the problem. Now you have to drive traffic to your FB page to drive traffic to your product page. So now you're effectively filtering your potential customers through another level. End result is you loose a percentage of possible visits.

In marketing there are primarily 2 approaches – shot gun and rifle. There are variations on either approach as well.

FB is the shotgun approach and Google ads is the rifle approach. You need to allocate a budget and then develop a marketing campaign/strategy that uses both approaches. Shotgun gets about 25% of the budget (if any) and rifle gets the rest.

When you're selling products spend most of your time and money on SOE – search engine optimisation. Everyone looking for a something to buy uses a search engine. They rarely stumble across it. Most people see what the want in the offline world then go to the net to research it. That should give you another clue about how to market and promote.

I can't be much more specific than that without knowing what your business and products are.