Jimmy Akin’s book above is supposed to be very good. The Four Witnesses by Rod Bennett is very readable. Mike Aquilina has a very good intro also, called The Fathers of the Church.
Jergens’ Faith of the Early Fathers is a Catholic reference set of books. Basically, if you need a quote about X subject, you go and look it up in the index in the back of Volume III, and you can find all sorts of things in all 3 volumes. (Obviously the Volume I index only covers Volume I, the Volume II index covers I and II…) But yeah, it’s a book of miscellaneous quotes, from various Fathers in chronological order.
Same thing with the Bible commentary series mentioned above – it’s just bits of quotes. Handy, useful, but eventually, you really need to read the context of the quotes to understand the Fathers’ thoughts.
If you want to start reading the Fathers in bigger chunks, for cheap, you can read translations of most of the important works on New Advent or
Tertullian.org (which is run by Roger Pearce, a very nice UK evangelical computer guy).
Archive.org and Google Books have plenty of other works, too.
When you get to the point that you need to compare translations with the original languages, or you need something that hasn’t been translated, there are all sorts of series collecting the Fathers en masse. Migne’s Patrologia Latina and Patrologia Graeca are probably the easiest to get online, because they are public domain; but he didn’t have the benefit of modern scholarship, and sometimes the printers messed stuff up.
Roger Pearce has a blog with links to pretty much all the public domain Fathers’ series books, but you will need to go to a university or seminary library (or use interlibrary loan, or have university ebook access) for the more recent ones.
I don’t want all this to sound forbidding. The Fathers can be very fun!
Remember, it’s not like they’re dead and gone. They are alive in Christ, and they will be happy to teach you. They also lived the Christian life in a very worldly world. If you poke around a bit in their writings, you will be surprised how relevant and helpful they are. They all have very distinct personalities and talents, and you will soon find them becoming old friends.