First off, what are you guys calling "Improvisation"?
Over the past few years this concept has gone from the idea of working with what you've got on the spot by exploiting your personal knowledge, skill-sets and creativity to how much pre-set junk can I carry on me in order to show-off the next time I see more than two people on a street corner.
That said, stop loading up for bear every time you leave the house. It's ok to have a couple of things on hand like a Thumb Tip in your pocket and maybe even a couple of loops around your wrist, but there is absolutely no reason to carry 1001 packet tricks, two or three decks of cards (especially gaffed decks), pulls, etc. UNLESS you are heading to a party or party-like environment and you know that the biggest reason you were invited was to give a FREE show. . . and as much as you may not relish that thought, this is how most of your friends & associates will see things, after all, tricks are for kids. . .
Stevens Magic Emporium had a series of videos. . . I'm not certain if they've been digitized and placed on DVD and may still be on VHS format. . . but they featured guys like Burger, Malone, Mullica and Kornhouser demonstrating genuine Improvisational Magic as well as Bar Magic. It was a most excellent resource as are the manipulation videos put out by Jeff McBride and for the very same reason -- these are things you can use at the spur of the moment and without uttering those 8 horrid words so many "magicians" lean on, "Sure, do you have a deck of cards". . .
The other side, as I've hinted at, is learning to use your own imagination coupled with knowledge. . . how many of you have done the Zombie Baked Potato? You only need a cloth napkin, a fork and of course, the potato (though a dinner roll can substitute the veggie) this was a classic table-bit in the 80's
Chink-a-Chink/Matrix was done with sugar cubes and bottle caps long before we started doing it with cards, coins and specially made items, then again you always have the classic one in the hand and one in the pocket type gags.
FOR THE MENTALIST AMONGST YOU there is absolutely no need for carrying a single item outside of maybe a few business cards done on thin card stock (for Billets) and a couple of normal writing implements. If you have studied and practiced Muscle Reading you have more than enough to do a solid 20-45 minute demonstration provided you have the balls to just do it and maybe even fail here and there. Second to this would be good People Reading skills, with little other you can create your own church (many have). By having these two skills a bit of knowledge when it comes to verbal & psychological forcing methods, you can blow people away at the drop of the proverbial hat.