Lube your chain! I know, incredibly basic and not a tip except for other new/intermediate people like me, but what a huge difference. Did mine because the squeaking was getting annoying, and it made a big improvement in ease of pedaling too. Must be a 10% (or more?) improvement in efficiency. Wish I had done it months ago, & of course the squeaks are gone too.

Another one, if you are thinking about getting a bike computer check out bicycle smartphone apps, it may do what you need. The one I use does distance, max speed, average speed, total time, total active time, elevation change, and records the route as well.