A lot has been said in this thread. Aero means a lot. Position means a lot. Structured training means a lot. Equipment means a little.
While all these things are true, recently my approach has changed a bit. Previously I kept adding gears. What this allows is for you to ride a broader array of conditions in your preferred comfort zone.
I now have discovered single speeds. These may seem a quaint, backwater novelty to most but, what a single speed does for you is rip you out of your comfort zone. You either get strong or you don't go. The ride is much more varied. Light load & 130 cadence going down. 500 watts @ 60 rpm going up until you explode.
A single speed set your preferred cadence at your preferred speed & letting terrain dictate your level of "discomfort" can force a lot of adaption.
Now that I've the light, I'm never going to not have one in my stable.
Try it. You might like it.
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I shouldn't have to "make myself more visible;" Drivers should just stop running people over.
Car dependency is a tax.