I'm pretty new to this whole ultra running malarchy, but one thing that I seem to have done quite well with in my short time running is my kit. More so than with shorter distances, choosing the right kit for you is incredibly important if you want to complete your run in the most comfortable and safe way possible. If you've ever had a blister, you know how annoying and painful it can be. Now imagine running 90 miles on it (yep, I've done that). But blisters don't have to happen if you find the right combination of footwear. Ever been caught up a mountain in shorts and a t-shirt and it starts snowing (yep, I've done that too)? Should probably have prepared for the weather turning.
I often see the same questions being asked by people looking to get into the sport; "Which shoes/socks/bag/jacket/etc. should I use?". In my opinion, the answer to all of these questions is very simple; "Whatever works for you". Everybody is different and what works for one person may not work for another. I have bought several items on the recommendation of people telling me they were perfect for what I needed, only to find that they really did not work for me. But it's no biggy - I just tried something else. Eventually you will find something that does exactly what you need.
Personally, I am generally something of a frugal (read "stingy") runner, so I try and find cheap equipment that does the job where possible. Also, once I find something that works I pretty much stick to it; "If it ain't broke..." and all that. I thought that I would do this post to go through some of the kit that I use, but concentrate more on my reasons for choosing the kit that I use (which hopefully will help if you are trying to decide what you are looking for), rather than what I actually use.