A candyflip is quite an experience, and usually a rather confusing one. Candyflipping can make you feel the MDMA empathy for the LSD cosmic psychedelia, can make you forget that time and space exist, and leave you playing in a ludicrously beautiful realm of abstract pretty candy colours, or it can also make you feel as if the incredible stress of your jaw clenching is warping the fabic of spacetime, your pants won't stop arguing with you and you can't find the floor anymore.
Candyflipping is not recommended for first-timers or the nervous. For your safety, take low doses. Do not try to push the boundaries of your usual dose of LSD. Standard disclaimers apply about not tripping if you are emotionally upset or mentally ill. But then, you should also know that the legally and medically recommended dose of both of these drugs is zero.
There seems to be a body of opinion in favour of taking the LSD first, often with the best time around 30 to 60 minutes before the MDMA, but you will hear other views. Illegal drug taking is by its nature a murky area. There is no right way to do it.