I'm gearing up to do several century rides this summer and hopefully put about 5,000 miles total on the bike (more if I achieve my car-free goal). I'm doing this on a shoe-string budget, so I won't be able to get any sort of power measuring device.

Currently my only metrics are current speed, max speed, and distance (as the average speed is way off because of city riding). I don't think I'll be able to get a HRM, possibly I can score a cadence meter though.

Most of what I have seen on training for improved performance has been on heart rate zones and intervals. I have been working on doing some HIITs, but not much more than powering on hard until I can't anymore than taking a very leisurely ride for a mile or so until I'm prepared to do it again.

Any tips on bettering performance without having a lot of data to work with?

If you just want to be able to ride a century, you don't really need anything, just ride lots.

It's a little more than that. I could likely ride a century right now and have been adding more miles per week since winter ended. Over long distances I am pretty slow or burn myself out to quickly. Ultimately, I want to be a better rider and be one of the early finishers for the century rides

At this point in your cycling "career" you are still better served by just riding a lot. You may need to work on your pacing if you are burning out too quickly. What kind of distances are we talking about?

One thing i have learned from my short time with a power meter is how much harder i go over short hills than on the flats. Even if i really concentrate on going easy on the hills, something about short climbs really messes up my perceived exertion. These short hard efforts really add up on long rides and leave my legs dead.

So, my one piece of advice would be rest on the uphills. Accept being in a ridiculously low gear going painfully slow. As soon as you crest the hill, you should be ready to wind it up again. If you ever feel like you need to ease off and recover at the top of a hill, even for a few seconds, you went to hard.

Note however, that this strategy is at odds with trying to stay with a group or in a paceline. If you instead choose to try to stay with a group, just make sure it is one that is not above your ability. It is very easy to get sucked into working much too hard to stay with a group that is too fast for you.

Yeah, use all the basic rules, like hard/easy days. Mix up your routes so that you climb hills as well as you ride flats.

Really, all the basic stuff will get you pretty far. Gotta have a "long day." Gotta do Intervals......