Christopher has the plan. . . especially if you think yourself a "Mentalist" in that we rarely need much more than what the brain can contain and one or two "basic" skills like Muscle Reading and Cold Reading techniques. However, I do tend to carry an SUC type wallet with me most of the time in that I use them in a manner that is NOT the usual peek wallet method. I frequently have my trusty Butterfly pad in my shirt pocket and my Mau Tou pendulum. I have a few habits of sort that require me to have several bits of paper, business cards, etc. in my pockets but I'll not go into what that's all about. But as a general rule, all these "extras" are for just in case moments in which I'm asked to perform and it becomes more than just a short demonstration (if I build a tip I will do more time).
Most people, at least in my day, moved into Mentalism so they didn't need to walk around a the Swiss Army Knife Magician, pockets overflowing with stuff. Like I said, Christopher has hit an important nail on the head here for others that want to be an actual "Mentalist" vs. being a magician that does mental styled material. However, magicians can take this same minimalist approach if they just educate themselves on what can be done totally impromptu with borrowed items; coins, shoe strings, finger rings, currency, match books, lighters, pens/pencils, etc. at most you will need a Thumb Tip and if you really have the addiction, a deck of cards. Granted, you can wear a few loops and even a gaffed finger ring or two or an expensive trick watch but it's totally unnecessary.