You could use general terms like:
* A bunch of mangoes
* A pile of mangoes
* A basket of mangoes
Or, you could get creative and come up with your own! For example:
* A blush of mangoes (referring to their rosy color)
* A symphony of mangoes (referring to their diverse flavors)
* A sunshine of mangoes (referring to their bright, sunny color)
Ultimately, the best collective noun for mangoes depends on the context and the specific effect you want to achieve.