Requirement of an SEO Expert for handling SEO of an IT Company website

We are an IT company and our expertise are in Website Development and Mobile App Development. We don't have SEO knowledge and our requirement is for an SEO Expert person who can handle the SEO of our website - [login to view URL] The website is ready with the proper design and content but still if there are any modifications required in the content then SEO person needs to handle that as well. And if there are any modifications required technically or in the development then we will handle that. Our clientale is International and Top targeted locations are Europe, USA, Australia and India. The website URL is - [login to view URL] Our monthly budget is 300-400 USD --What results we would expect ? --What will be the expected time for the results?