It has been my experience of 30 years teaching them that it's easiest to learn them in groups. Because they are in groups. Just like the World Cup. The group of no change verbs, the group of "i" in the present, "a" in the simple past, and "u" in the participle. The group of "___ought" for the simple past and the participle. I think that learning them a, b, c, according to the alphabet isn't as exciting. You do find them exciting like me, don't you?
The most important thing to remember is don't bother learning the other 300 irregular verbs we have. Don't even think about them. We never use them because they are too old. So just learn the 85 or so you find in the good grammar books available now.
Best of all, English is a forgiving tongue; if you make a mistake people will understand you OK, and if you get it right people will know you studied hard and had a good teacher like me.