Hi, Even! As far as certifications go, a plain Open Water cert typically covers you down to about 40'-60'. Advanced Open Water typically certifies you for deeper, 70'-100'. I think most agencies require a "Deep Diver" type cert to go that extra atmosphere of pressure down to 130', which is considered the limit for recreational diving.
Of course, technical certifications and the right gear can get you beyond that.
How deep you "typically" go depends more on where you are and what kind of diving you do. Here in Florida, reef divers, spearfishers, and lobster hunters are typically at depths of 30' or less in the Keys, to 90' or so off Jupiter and the east coast. Wreck divers have plenty of options in those depths, too, but there are also many wrecks at 150' or below accessible only to technical divers. Recreational cavern divers typically stay within 100', and of course technical cave divers are another category unto themselves.
Regarding your question about light, as a reef photographer I have found that, on a bright sunny day, I can take some nice pics without even using a flash at Keys depths of 15' or so. Much deeper than that pretty much requires a flash.
You don't really need a light to see well enough to dive in any recreational reefs during the daytime, but below about 60' it's often handy to shine one on the reef to see the colors (which otherwise all wash out to blue-ish) and to look under ledges for the life under there.
Long and short of it, I would say my dives average out at about 50'. I rarely ever go below 100'. I think this is typical for Florida reef divers. As far as light goes I always bring my camera flash, and I always bring a dive light, even though I might not need them.
Does this help answer your question?