Hi, my name is Ayub
In my opinion, when you want to build a website, you have to follow this step :
1. Setup goals of your website. You have make it clear, and for the beginning you have to focus on one idea. In here, you said want to build site like Freelancer.com. It's clear, you want to create working market place that will connectiong Employer to Freelancer.
2. Setup requirement data for content. You have to set what kind of content on your site. For your case, it seems you need user profile data, bid, project details, etc.
3. Paint your web design to deliver information from data. Search designer, tell him your idea and provided content. Let designer convert your idea to UI/UX design. Because you want create sites like Freelancer.com, you have to need professional and elegant design with very light load design. It also need create mobile version for mobile or web app.
4. Choose best platform and search for review. Maybe your case has to be done by other people. You can learn from it, what is the beneffit and disadvantage from his website.
5. Development. You can say it, convert idea to website/app. It has to be clean and readable code. You need programmer here.
6. Create alpha & beta version. Alpha to check and create additional feature for next version. Beta to get feedback from users.
7. Deploy and release, now your website/app ready to use.
8. Optimize your website so it'll always exist. Need SEO expert.
Thanks, we can discuss further via WhatUp or Skype.