http://animania.eclectic-world.com/post.cfm/sailor-moon-essential-episodes
For all the people who have or will try watching the anime and ever find themselves bored with the filler episodes. This helpful guide points out all of the key episodes, and episodes were semi-important events happen, like the first time a new attack or item debuts.
Filler isn't inherently bad, it really depends on the show. And in this case people find Usagi to be the least interesting of the senshi, so having to wait until episode 8 for someone else to appear can be kinda taxing.