I see so many comments about people spending a ton of money on their kit, and I have to say that always baffles me slightly. I mean, I know what the paychecks I take home look like, and I can't afford to go dropping a ton of money on my kit. However, I don't like the idea of not being well supplied either. My solution? Free stuff.
Seriously, how many times do you get free samples of things? Every free sample I get goes into my kit. If I need something, I go out to product manufacturer's websites and order free samples. Last time I was at my dentist, he gave me a whole bagful with every sample they've got of toothbrushes, travel sized toothpastes, dental floss in handy travel containers, a couple things of mouthwash, etc etc. When I tell people what it is I want the free stuff for, people get really excited and want to help out. I don't think I could tell you when the last time I actually bought something for my kit was.
Honestly, though, think about it from a manufacturer's perspective. When they give free samples, the idea is so that you can try the product, fall in love, and switch. How much better does it get than if you tell them, "I can put your product in the hands of ten, fifteen actors in the next month, and all it will cost you is a trial-sized version of your product. Don't want to give me free things? That's fine. How about coupons or other discounted offers? After all, in a sense, I'm doing advertising for you..."
Speaking of, I need to go cruise toiletry websites again. I'm low on sample-sized deodorants...
Edit: I did think of a couple things where I will go buy supplies. Obviously, the hand tools I've got and the first aid supplies I can't get for free are ones I've purchased, but anything consumable I try to get for free. I'm working on ways to get the first aid supplies at no cost, though. If I could do that, I would probably not have to buy new stuff ever, unless it goes missing.