You might consider reading some bike training books, just to get an idea of how some folks do it, then modify the plans to fit you.
A good base is definitely most important. I find that as a relatively new (about a year) roadie, and a middle aged one besides, that I needed to spend a lot of time just slowly increasing my distances. Now I try to vary my routines by riding some days mostly long and flat (up to two and a half hours), and some days more hills but less distance (up to one and a half hours). Eventually I'll put the distance and hills together. The other factor, of course, is how much time you have to train.