right now I'm starting a small business and when dealing with facebook page and instagram for business, with their offer of boosting the page or advertising, how effective is it for small business? is it necessary? with all the questions from facebook about the market segmentation that i want to reach, how to manage to get best result? Thank you.
Assuming you are in B2C - Facebook and Instigram are not effective in B2B - you should find a seminar/training class before you go very far. If after that you think you are ready to do it yourself, start slow and use tools that will tell you about. You can blow a ton fast and get zero. However if you think you need outside help, these classes will help you sort out the bs. Before you start anything though be clear eyed about what your product/market fit and absolute clarity about the individual personas of your target. Build detailed lists of personal attributes including income/interest/age/politics (if even they are uninterested). This will often give you the answer. Do not let FB or Google internal people do his for you. They are not on your side.
My personal experience has not been positive with using paid adverts on Facebook. I got a lot of reach and page/post likes (depending on the campaign objective), however none of those likes led to conversions till date. When I saw the profiles of the people who liked my page or post based on the advert, I have a strong suspicion that they are fake profiles.
The other side of the story could be that I was not using social media marketing appropriately, especially when defined the target audience. I have tried many variations all with the same results. I will suggest reaching out to social media marketing experts if you know anyone personally and taking their advise on this