This lightweight theme is made in Canada, has fantastic support, easy to use and fantasic price! GeneratePress
While you don't need a page builder to use WordPress, especially with the new Gutenberg blocks built in, it can speed up development considerably.
My favorite page builder plugin is Elementor. It's powerful, easy to use and reasonably priced. Free or Pro versions. Elementor
Plugins are plentiful. It can take some research and repeated use before you find some favorites.
Code Snippets is one of the first ones I install on a site. I use it to create custom code snippets in PHP. They can be used like "mini-plugins", turned on and off, and are really lightweight.
Tiny PNG is an image compression plugin that will ensure your images are shrunk to the smallest possible size for loading on your website. This helps page speed.
Woo Commerce is my e-commerce platform of choice for online stores. There are numerous plugins and extensions.
Wordfence is a security plugin that helps monitor against malware.
WP Show Posts is a lightweight plugin to make mini blog lists. You can put these anywhere on your site easily.
Facebook Cover Photo 2018: width:height ratio is 16:9. 1920 pixels by 1080 pixels is a good size and will display nicely on all devices. Make sure that faces, text or important info is towards the middle of the image so that any cropping won't be noticed.
Louise M. has updated template sizes to help if you need more details.
While a developer can quickly get you up and running on a platform of your choosing, sometimes you want to try it out for yourself. Here's a good document about the pros and cons of each of the most popular website builders in 2018.
My preference to date has been WordPress for it's easy maintainability, quick development and customization.
Coolors.co is a really smart color palette generator. You can lock in colors you are already set on, and generate complementary colors to them!