Would it improve the performance of my XF board if I set up a cache, as described in the XF manual? If so, what kind of cache back-end is recommended for a 1G or 2G VPS? (The manual mentions File, APC, and Memcached, but it doesn't say anything about system requirements.)
Also, what kind of data is actually cached? The manual mentions user sessions. What else? Most/all of the pages are dynamic, i.e. displayed differently depending one who is viewing etc, so how much can really be cached?