I've tried using pre-built templates and themes before but once I've finished modifying them to match my content, they don't look as good anymore. The thing that works great for me is to just use standard, unmodified bootstrap. It stops me worrying about the design and everything looks presentable. But now the project is nearly finished and I want to customize the design a bit.
https://bootswatch.com/ is great. Are there any others people can recommend?
So my advice would be start with an design or idea and after that is done start coding.
It exhibits the materiality.
If you don't like the way Bootstrap looks, use a different material.
Or rebuild your content to the material.
That's design.
The rebuilding. The doing it again, I mean.