Don't use a css framework unless you don't know how to design or don't have a designer. In my experience, you end up stripping out/overwriting more than the help it suggests it provides.
Also, from concept start to final product, the process is extensive. There are plenty of resources online, but boiled down > start with a concept, research/validation, wires/prototypes, test/reiterate, design exploration, design, test/reiterate, dev, test/reiterate 10+x, release, repeat. Missing a bunch of details and likely steps, but that's the gist.
Ah word. Yeah then ain't no shame in using a framework, but give a shot at styling based on design inspirations you find. Design's just another system with rules.
Also, from concept start to final product, the process is extensive. There are plenty of resources online, but boiled down > start with a concept, research/validation, wires/prototypes, test/reiterate, design exploration, design, test/reiterate, dev, test/reiterate 10+x, release, repeat. Missing a bunch of details and likely steps, but that's the gist.