I got back on my old bike several months ago, and have been riding around the neighborhood and local trails at a moderate to easy pace. Just before Christmas, I was riding at least three days a week, about 7-10 miles, at around an 8-10 mph pace.

I picked up a new road bike, and have noticed that I can go much farther, and a bit faster with less effort. By spring (March) I would like to be able to ride 25 mile, 16mph club rides.
I have ridden three days this week, plan to ride tomorrow as well, and take the weekend off. I rode one day a bit light, skipped a day, the next was an average day, and today I pushed pretty hard for a bit more speed and half again my normal distance. Tomorrow I plan to ride at a relaxed pace, but to put in as near my normal distance as I can.

My plan was to slightly increase the distance and speed each week, with a similar schedule, weather permitting, so 4 of the 7 days.

Is it best that I increase the frequency of my rides, and gently push the pace? Should I stay about the same, but increase my distance? Do both? Ride one or more hard days a week with the same rides for recovery inbetween?

My story: I would ride 5 miles at one time. Rest at my house, then 5 more miles. 40 miles one day.

Took 500 miles to feel my legs were in shape. 1000 miles for legs ready to go fast.

You will get stronger the more you ride. Have fun be safe.

Go slower on days that you're riding long, and faster on short rides. Faster when you feel good and slower when you are a bit tired. Pretty simple.

Try working up your distance so you're doing 25 mile rides before you try the group ride.

You need to do it all, yet ease into it. I titrate it by weekly mileage. If you want to ride a 25 mile club ride, averaging 16, that's a long way from where you are now, mostly because club rides tend to go up every hill in sight. I'd say if you were riding 50 miles/week by March, you'd meet at least some of your goal. Meaning you'd get the 25 miles just fine, but maybe you'll get dropped and limp in. So be sure to get a cue sheet or know the route some other way. Getting dropped is normal. We've all been there, many times.

So get out a calendar and plan your weekly mileage between where you are now, and where you want to get to. Increase it at a steady percentage rate each week. Then space it out into your different rides. Plan it all out. But having done that, don't fixate on it. Be ready to change the program completely. You don't know what your response will be. Maybe that'll be too little and you'll want to do more, or maybe it'll make your back sore and you'll have to back off.

You'll want to ride hills at least one day a week. You don't have to actually ride all the way up them at first. Just ride until you can't and take a little rest. But hills will make you stronger and give you more endurance than anything else.

Just ride, and enjoy yourself. You'll soon find out that 25mi. isn't all that far. Don't be afraid of hills. They will make you stronger. Your speed will increase along with your endourance. I'm not sure what kind of group you plan to ride with, but the one I ride with will wait for anyone who gets dropped, yet we still have plenty of time to get competetive. A word of caution "cycling is addicting"

Ride lots and don't over analyze it. Focus on having fun and seeing the sights for a couple seasons, rack up the miles over varied terrain. After that it becomes pretty clear what you'll need to work on.