I am just wondering what advantage do you see after clearing the cached contents from RAM? Seeing a lot of Free memory is not really shows its all good, especially when its showing after clearing the cache. Clearing cache will free RAM, but it causes the kernel to look for files on the disk rather than in the cache which can cause performance issues. So its not recommended to do it regularly. When there is an increased demand for memory kernel will automatically clear cache and allocate RAM for the requested process.
if your server is getting low RAM you need to find the reason, clearing ram is not the solution
if you have added more websites to your server
or if you have added some plugins to a site
or any modification you have made that cause the server to use all the RAM need to be considered.
Once you find the reason you probably can fix it or optimize it, or BUY more ram maybe that's what your server need because you have added more sites or your sites grow in traffic considerably.
In your case I will say if possible please try adding a 2 G swap which will help in load times. Normally there is no actual use in clearing the RAM as those which are showed as cached is also available for processes. So it will get cached again after some minutes or hours.