Streaming over the Internet via addons such as Cimema Experience, Cinemavision and HGTV is dependent on the speed of your Internet connection as well as all points between you and the remote server. Therefore, if the streaming speed is generally too slow, then caching isn’t going to help.
That said, you have nothing to lose from trying to increase the cache size. Take a look here and see if it helps. The advancedsettings.xml file should be found (or if not there, created) in directory /home/osmc/.kodi/userdata