Best solution for public shop I want to create a site where users can sell their products. 

How best to do this kind of system? 

Is it a good idea to use Ubercart or it may be better to use something else?
You have got two options. Ubercart or Drupal commerce With Ubercart you have to do some bits of configuration to get your store ready.

With commerce, you have a basic store setup for you if you use the Commerce kickstart distribution. 


  Commerce Kickstart is the quickest way to get up and running with
  Drupal Commerce. It includes the latest versions of Drupal core,
  Drupal Commerce, and the other modules it depends on. It also gives
  you a set of options to create a fully-featured demo store out of the
  box complete with an attractive theme, catalog and search
  configuration, and a custom back office interface.
  
  Who should use Commerce Kickstart? Anyone who wants to skip weeks of
  configuration to build a commerce site on the Drupal Commerce
  framework.