Imo, you should start slashing to get a few MQ's, get a feel for the game and along the way, check out the different guilds you slash with.
There are many out there whom I've slashed with that are very nice and supportive of new players.
You wouldn't want to join a guild, only to find out that they do private runs with only the higher ups.
Trust me, a bit of slashing with random guilds, and you'll definitely be able to tell which guilds are more worthwhile.
