The information available can be summed up fairly quickly:
First, the Medieval material: The story of Taliesin, with its variants; and various medieval Welsh poems which refer to her cryptically. For Taliesin, Patrick Ford's translation of the Mabinogion is readily available secondhand and has a translation the main original text; his book on Taliesin (if you can find it - it's like hen's teeth) has more variants. Charlotte Guest's translation is available on the net and gives the essentials, though some details are different. The poetry is mainly in the Black Book of Carmarthen, of which there's a poor translation (Skene) on sacredtexts.com. But for a good summary, I'd go to Jan Fries, "Cauldron of the Gods - a manual of Celtic magic" (one of my favourite "Celtic" books) which presents a good range of the material and asks you to make up your own mind what it means.
Second, Robert Graves, who decided to take Ceridwen as the crone aspect of his triple goddess, equated her to Hecate (who was never previously a crone...), made various other links, e.g. the sow connection, on what seems to me to be tenuous evidence, and set off the modern fascination with her.
Lastly, there's material produced subsequently by her modern worshippers - for example, your dragon-rider stuff. Judge for yourself!
I find Ceridwen a very intriguing figure. Clearly she was important to medieval Welsh poets, who associated her with inspiration, and can be interpreted as referring to her as a goddess, even though they themselves were Christian. But if you're after a historical view of her, the evidence is tenuous; in the end I think you will have to work out for yourself who she is to you.