I've also read in doing a ton of research before receiving my Russian Tortoise (today actually) that it seems most people keep it between 50-60% mine is at 55% right now. I keep checking it being the nervous first time mom lol.
I usually keep my two Russians around 50 to 60 but have had a drop this winter to 30 to 40 do to the really dry winter were having. I am always pouring water into my enclosure. I also have to add water to my aquariums every week cause they drop an inch or more and they are totally covered top with small cut outs for filters and stuff.
Here's a photo of my air bubbler humidifier. Its made from and aquarium air pump, some hose,an aquarium airstone and a plastic container. It adds lots of humidity and costs ten bucks. Semi closed chamber. The gauge showing 76%.