Replying to Domain Registration and Website Building

I recently I have been looking into and some basic research on building a website for my business and realized I have no clue what I'm doing. I know that the web address I want is available but I don't really know what to do from there and I don't want to run into any scams or get screwed for jumping into something I know nothing about. Can any of you give me some good advice on the do's and don'ts of creating your own site? We're talking basic ass stuff like which company should I buy the domain name from? What are some cheap options for actually building the site myself? Is it feasible to make a clean looking professional site on a budget and with no knowledge? Is it worth it to buy the domain name from a company that provides web building features? Generic other question that I don't even know that I should be asking?

If it helps, I have a business doing sustainability consulting and energy conservation. It's just me (sole proprietorship) so I have like no budget for hiring a website designer. I want it to, especially at first, be very basic and clean looking since my portfolio is quite small and almost non-existent at the moment.