Graham bemethavinci You need to understand basic html before anything without html you have no site html is the scaffolding that holds everything together
Next is basic css how to set colors backgrounds and and borders how to create a stylesheet and link it to your html understanding how css can be built up using multiple stylesheets (hence the name Cascading Style Sheets)
once you have a basic understanding of html and css you can start worrying about stuff like javascript twig jquery xtscript
and all the other scripts and stuff
as for Bootstrap it is just html and css with a bit of javascript thrown in and there are certain things you need to create that framework or it just does not work correctly
its like building a house you have to start with the foundations and work up or everything just falls apart you keep trying to put the roof on before you even have any walls to hold it up