#1. Be different. Try to offer something the other, bigger guilds don't have.
#2. Do something insane. If you cause an upset, like stealing/breaking a defended RP from 2012 for example(please dont!!), your status would increase a little and help with recruitment.
#3. Become friendlier to a larger guild. They will typically receive 2-3 people a day wanting to join them! If they are acceptable we'll take them. If they are borderline, we'll send them to our sub. Anything below that and we might suggest a few other places they can try. It wouldn't make you into a sub or filter. I've sent a few players off to guilds that are hostile towards us, simply because they wont be accepted here and those enemy guilds are actually more suitable.
#4 Quit your guild and consolidate into another. There are many guilds who are active but like yourself, have 3-4 people. consolidate a few into one and you'll have lots of members and more ability to play. Takes a lot of talking and kid-drama to achieve.