Newbie here, wanting to upgrade but unsure where to start

This comment was posted to reddit on Dec 25, 2022 at 4:16 pm and was deleted within 13 hour(s) and 52 minutes.

Saddle has to be adjusted; the choice of saddle will reflect on what kind of riding you do: casual cruising or performance?
Besides the saddle, try adjusting the height because a seat too low is going to cause some hurt on the legs and knees when trying to pedal longer distances.
I'd rather keep some of the reflectors, even with headlights and taillights -- better to have double the visibility at anytime, as well as a fallback.
switching to a different drivetrain has its pros and cons; 1x9 or something like that may simplify bike operation by eliminating the front deraileur and reducing weight, but asides from the cost of retrofitting (like going for a completely new set of hubs, and trying to wedge 135mm of axle into those rear dropouts), some regular inspection and maintenance is also needed to ensure smooth operation.
front or rear racks, basket, or at least a handlebar bag, especially if you must ride out for groceries.