Light Armor + Archery + One-Handed + Sneak. Maybe Alchemy on the side.

NOT thief. Ranger as in, you only sneak in to ambush with a bow. You DO NOT try to run from aggressive combat, you go to it. Try to bow and arrow everyone, then fight with one-handed sword when they close in. Best thing to do is to have a tank follower.

Best armor/guild/weapons? Tips, suggestions?

Perhaps Thieves guild for Nightingale, but I don't think it fits in well with thieves.

I'm currently playing one. I started with a goal of...just sneak and shoot form a distance.

I collect every ingredient I come across and even go on exhibitions for River Betty.

The character just evolves on it's own.

The problem I had with this kind of build was that the sneak archery was too powerful and I kept killing everyone before the battle started without trying.

The staggering with Power Shot is really great for slowing down your enemies while Kiting. Ranger perk is really powerful for keeping mobile while fighting with bows and it's almost too good. I recommend it for your Ranger build. Critical Shot is also exceptionally useful in open battle. It allows you to stagger larger monsters that are normally immune to stagger.