Data sharing between Android devices over the Net

I am developing Android apps which allow users among other things to share data (chat, images, large data files) over the WEB. Does anyone have advice on how to achieve this ? The main requirement is low expenditure , at least initially. The functionality would be similar to that embodied in an App such as MyTrails.

I have developed a suite of tools for developing ,testing and debugging intercommunication services between devices, but I’m not sure about the best way to proceed on large scale communications,

Thanks to anyone who can help.