The truth is that someone can get started with very little, and most of it is readily obtained. One can construct a lean-to shelter out of long tree branches and a white canvas paint drop cloth obtained at a building supply company. An example of one is shown in the picture, this is the actual first encampment of a friend of mine. You might see one at a rendezvous occasionally. Go over and take a close look at how it is set up, the owner will be happy to explain how he sets it up and what materials he uses. Even though it looks very humble, this is actually closer to what a mountain man would have constructed for himself at rendezvous . The pyramid style tents that are commonly used at rendezvous are reproductions of miner's and/or military tents which existed close to that time period, but it would be unusual for a mountain man to haul around such a heavy bulky item, and it would make him very visible to some of the Indian tribes who were less than pleased with the white intruders. Their use at modern rendezvous is more a concession to comfort and convenience rather than an effort to be historically accurate. And it is quite common to have a modern camping area at a rendezvous a short distance from the primitive encampments, where you can use a modern camping tent or R.V. (we mountain men call them "Tin Teepee's!") until you get a primitive shelter.
Clothing can be simplified for someone who is starting out. Some of the pieces of clothing that are never acceptable are blue jeans, t-shirts and modern "sneakers"! White painter's pants with the loops cut off comes close to canvas pants of the time period and are acceptable. Corduroy pants were available in that time period, and are also acceptable. Simple store bought moccasins are acceptable. At many rendezvous you can purchase an appropriate drop shoulder shirt, or patterns for them are sold there quite often. You'll also find patterns for buckskin pants for when you're ready to try your hand at an ambitious leather project. Sometimes you'll find someone who is selling the leather, too.
Most of us aren't very quick to admit it, but many of us do have modern things in our camps, hidden under blankets or canvas covers, or cleverly disguised. If you need to use something modern, like a cooler to store your food, improvise a way to hide it from direct view. Don't feel you are compromising, some day you'll find out a lot of those large wooden boxes in camps contain insulated coolers!
Patience is a virtue for this activity, believe me! It's almost impossible to accumulate all the equipment in a weekend, or even six months! But the items needed to begin mentioned above can be obtained fairly quickly, and nobody will look down on you for not being as well-equipped as some of the others are. We want you to be involved, and seeing your progress at each rendezvous makes us smile, as we remember our early days at rendezvous. If you would prefer to get some good information through a book, I would recommend "The Book of Buckskinning" Volume 1 by William H. Scurlock, available through Amazon.com, and perhaps some larger bookstores.
In a way, it's good that the equipment requires time and perhaps a bit of elbow grease to get together. You'll meet some fine knowledgeable people as you ask questions, and you'll have a good memorable story behind each item you get. Never be afraid to ask! We've all been beginners at some point.