How do I get faster?
I know...ride more. I have been riding for a little over a year. Just recently stepped up to longer and more frequent rides. I had been doing 2 10-15 mile rides per week on average. In the last two months I have been doing 3 15-20 mile rides and 1 40+ mile ride per week. I do a fair amount of climbing. My shorter rides average 750-1000 feet gain and longer ones around 3000 feet gain.
My average speed is usually around 15 mph on my rides. I usually ride solo but I want to get into some groups. Where do I start to get myself up to the 17-18 mph average? My only plan is to add hill repeats one day a week instead of one of the shorter rides. I am pretty clueless on cycling training