A very easy way to speed up the front end development of your website is to a) use a decent UI framework (Bootstrap being the obvious answer here but there are others) and b) buy a theme that's based on said framework. Descent themes normally come with a variety of different layouts giving multiple options for your website (e.g homepage, blog & search results). You can then select which parts you like, move them across to your website and ignore the rest.
A side effect of scaffolding your website in this manner is that you normally have no choice but to include the full CSS file that came with the theme (unless they've kindly separated it out into lots of smaller files using a pre-processor like SASS - this, however, is not the norm).
Large CSS files, full of redundant selectors, increases both cognitive overhead when making changes and the amount of work needed by a browser to to download and parse your stylesheet - not to mention making your code feel dirty. Manually cleansing the file would have been tedious and error prone, I was looking for a better way.
It looked like this:
Once that was in place, a simple call to "gulp uncss" kicked off the task and 10 or so seconds later (it's that fast) out popped a CSS file minus the selectors that UnCSS thought no longer appled.
After manually comparing both the old and the new files, the only selectors that were missed were the obvious ones on authenticated pages and a couple pertaining to interactions with the site (at the moment, you can't tell it to click buttons etc).
The best bit was that my stylesheet dropped from 54Kb to 14Kb (an almost 400% improvement) and most importantly shaved off a lot of complexity. Exactly what I was looking for!