What is the best website builder for a beginner looking to create a professional website?

I am looking to start a professional business website, however I have no knowledge of how to create a website on my own, and do not have the funds to hire someone else to do it for me. I've looked into WordPress and have watched a few instructional videos, but find it very confusing. I would like to create my site on a website builder to start off, and maybe switch to my own personal site in the future, but I am having trouble choosing which one to go with. I've briefly used SquareSpace in the past for a different project I was working on, but I don't know if there is a better option out there. I've researched different options and still feel lost!

Basically, what I want is a site where I can sell merchandise, have a blog, some videos, and maybe do occasional fundraising projects. I would like the site to look professional and work well on mobile devices (not sure if all website builders have this function but I'm putting it out there just in case =] ). I know that all businesses require an investment and I am willing to invest in paying for these sites, I'm just very limited on funds at the moment so I can't use anything that is way too expensive.

What site would you recommend to start off my business with? Thanks!