You can't upgrade your entry level road bike
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Only upgrade I truly appreciate in last 70 years was when Shimano moved the bloody bearings to the right side of sprockets. No more bent back axle. Nothing else comes to mind.
Correction: Maybe when Nokia made first studded tyre in 1966 was even bigger "upgrade". But this depends where you live.
Source: person who has biked to work for 20 years.