Don't expect precision. Here are some shades of meaning as I understand them (I'm a native U.S. speakers).
"He can get a laptop." This means he has the ability to get a laptop. For example, he has enough money. We would not be talking about whether he is able to get a laptop unless we believe that he wants to get a laptop. Therefore, to me, "He can get a laptop" means "he is able to" and "he wants to" and therefore I expect him to get one, probability much higher than 50/50.
"He could get a laptop." To me, this suggests that there are alternatives. He has the ability to get a laptop, but there are other choices he could make. He could decide to get a tablet or a desktop computer instead. It is quite likely that he will get some kind of computer, but maybe only a 50/50 chance that it will actually be a laptop. The uncertainty is not about his ability. The uncertainty is what he will choose to do.
"He may get a laptop." To me, this expresses general uncertainty. Again, maybe 50/50, but the reasons for the uncertainty are less clear. I don't know as much about the situation.
It could also express permission. This would be unusual but possible. "The university requires every student to have a Windows computer of some kind. Johnny was wondering whether it would be OK for him to get a laptop." "Yes, he may get a laptop."
"He might get a laptop." To me this expresses a lower probability than "may." It is actually less than 50/50. It's possible, but I don't expect it. "He might get a laptop, but knowing him I think he will want to install a second hard drive, so I think he will opt for a desktop."
But don't overthink it. We don't use these words with any great precision.