Hello Antonija, It really depends on the use you make of Dribbble! I personally use it as an awesome tool for design trends and UI ideas monitoring but keeping in mind that most of the shots integrate a small amount of functionalities... However, you can find some really great designers and agencies who publish real shots from clients work (ex: Balkan Brothers > very inspiring because they manage to combine minimalism and functionalities) ! ;-)

They should probably not choose any platform but their own. Buy a domain, make a website, share your work.

I'm doubtful designers use Dribbble for its community :/ Mostly a portfolio and inspiration site at this point (?)