I have 3.5yr of experience and have worked on multiple B2B and SaaS projects, but i haven't made a portfolio of my work. What type of portfolio should i build?

I have 3.5yr of experience and have worked on multiple B2B and SaaS projects, but i haven't made a portfolio of my work. What type of portfolio should i build? How many case studies should i put? And should i include some of my official client work in portfolio? 

Seeking your valuable advice.

Need meaningful advice for portfolio.