By merging themselves with other people, the user can grow tremendously in size and strength. Inorganic objects are also included in the fusion, as the merged form of the Charlotte Decuplets, who each wield a normal-sized scythe, carried a massive scythe, and wore clothes similar to a mix of the ones worn by the Decuplets.
The fruit seems to offer no benefit to the user if they do not have other people around to merge with them. Other than that, it has shown no particular weaknesses aside from the standard Devil Fruit weaknesses. 
Newshi mainly uses his fruit's powers to merge with his other nine decuplet siblings, turning into a giant creature wielding a very large scythe, which increases their fighting capabilities significantly.
Gattai (合体,Gattai?, literally meaning "Combination"): The Decuplets stand in formation next to each other and Newshi activates his power to fuse the ten of them into a massive figure armed with a giant scythe. It was first used while fighting the Vinsmoke Family on Cacao Island.
The Gocha Gocha no Mi's abilities are similar to the Jake Jake no Mi's, as both fruits enable the fusion of multiple people. The Jake Jake no Mi appears to be more limited than this fruit, as it only combines two people while this fruit can combine at least ten.
It’s also similar to the non-canon Gasha Gasha no Mi, as both involves combining objects, although the latter focuses on inanimate objects.