I'm in the process of going Samyutta > Majjhima > Digha
The reason for this order was that I've read (I think it was Ajahn Sujato who mentioned this) that generally speaking, textual studies show that the material of the Samyutta Nikaya is actually amongst the oldest of the Pali Canon, whereas the Digha Nikaya tends to be closer to the other end of the spectrum.
The Samyutta and Majjhima are great but for different reasons. I get the feeling after reading the Samyutta, you've really read just about all the teachings you'll need to read, whereas the Majjhima is a little better at contextualising them and is less repetitive, both of which make it an easier read.
However you approach it, I'd recommend you put the Digha last. It's very wordy.
Through corruption of the Dhamma comes corruption of the discipline, and from corruption of the discipline comes corruption of the Dhamma. This is the first future danger as yet unarisen that will arise in the future. You should recognize it and make an effort to prevent it. (AN 5.79)
Neither traceable in the Discourses nor verifiable by the Discipline, one must conclude thus: 'Certainly, this is not the Blessed One's utterance; this has been misunderstood by that bhikkhu — or by that community, or by those elders, or by that elder.' In that way, bhikkhus, you should reject it. (DN 16)