I am a bit too new with Blocs to give you an authoritative answer and hopefully somebody else will offer an opinion, but I think Blocs should be good for what you need as a novice designer.
In terms of building a nice looking web page and showing the images that should not be a problem. It would be good to decide on the billing platform in advance e.g PayPal or Paddle for example, since that will be a consideration in the design process. I sell online through FastSpring and it's simply a link to a web page, but some systems appear to involve more complex plugins.
I have a lot more experience with Rapidweaver and it's true you would be need various additional purchases before you could match what Blocs can do directly. It's also true there have been a lot of performance issues and various complaints about lack of support. Rapidweaver can do some things that are not yet possible with Blocs if you spend enough money on plugins, however Blocs is developing at a much faster pace.