First, how does factions work? I joined the Sensates because I wanted those sensory stones for free but I noticed when I asked the Godsmen about joining them and they said I had to leave the Sensates. Now I was thinking I should one that I feel relates to how I built my character and I can't say I found any that directly relates but Sensates came closes but I also want to experience as much as possible, gaining access to each factions' secret is a plus.

Second, about Ravel. OK so I found that barbed Iron thing that is suppose to teleport me to Ravel's maze but I'm a little worried. It says that I won't be seing Sigil in a long time, does that mean I won't be able to rest because I will likely die on the way but I haven't tried yet, I wanted to make sure I had done everything I could before venturing in their.

I always join the Godsmen because I like what they preach and they have an interesting quest line. You also have to join them first before you get the opportunity to become an Anarchist. As for the Sensates, you can get all their benefits from the Festhall without actually joining them. And other factions are more or less alignment-specific, i.e. you can't joun the Xaositects without being chaotic enough.

About Ravel: activating the teleporter sends you on a long quest line that stretches throughout several planes. You will only return to Sigil just before the last quest. You can rest in most new areas, though maybe not specifically in Ravel's Maze, but that part of the game is rather short, so just rest once beforehand.

You can join the Godsmen if you like, if they don't please you you can still change back to the Sensates or another one. Factions are unimportant anyway.

After leaving Sigil you'll of course be able to rest at some locations, it won't hurt being fully rested before entering a new territory however.
You will return to Sigil later and be able to do the quests there but doing them and getting the best equipment before leaving won't hurt.

Thanks for the tips guys. I will search some more before I travel to Ravel then.