I have also realised that cycling in low cadence made my muscles feel totally drained and cycling in higher gear was tiring me way too early ( fatigue). I found out today that I should stay between the 12-14th gear to be more effective on the bike.
That brings me to my next question - how do I improve my overall cycling ability? I cannot follow any training apps / coaches as I cant commit whole heartedly at this point. Any other natural ways to get better other than riding more?
Good stuff your stats look a lot more comfortable.
Speedwise you can make marginal gains, type of bike/ position, wheels, tyres etc but riding more (as long as you don't wear your self out)/ training has the greatest effect. I use the TrainerRoad app, I quite like how it adapts around me and my schedule and that you can take sessions outside. I miss quite a lot of sessions in the summer though as I'm too much into group riding for the social benefits.
As to cleats, they help with keeping your foot in the right place to deliver power so they will be a help eventually. There's no need to rush though.