I've found that there are various ways to "cheat" and create scenes that have more characters that RAM would allow.  One option that works for me is "stiching" together renders.  Basically you set up your scene without characters, and then mentally divide it into "zones" (such as "left side" and "right side"). It may help to use a simple prop to divide the zones.  You then only load the figures that would appear on one of the zones, and render the zone.  For example, if you have ten people lined up on a beach, set up your empty beach, then load the people who would be on the left side of your image.  Then, do the same thing for the rest of your zones.  If something would be in one zone but can affect other zones (for example, a light in zone a that shines onto zone b, or an item in zone a that's reflected in a mirror in zone b) load it in all of your zones.  The same thing applies if an item would overlap zones.  Then, once you have your rendered images, cut/paste them together in photoshop.