I've never left with any set amount of money in my pocket, and normally when I try to, I end up spending it all in a couple days anyway, cuz I'm no good at keeping to a budget. I've always found that you will be able to get what you need on the road if you believe you will. In repsonse to dilligaf2u2, I am talking about long trips, at least 4-6 months on the road, with breaks in cities and towns along the way to stock up.
I have no problem working for some extra cash along the way, and will normally fly a sign to the effect of 'Will work for food/shower/$$$'. Obviously you have to be careful who you let take you home, but I've never ran into any major problems. At worst, I've always found that if you park your sorry-looking ass outside a grocery store or something for long enough, someone's gonna come out with some food for ya, even if you haven't asked for it. This doesn't work for all people, but if someone offers me something, I'm willing to swallow my pride and take it. It's also just as easy to go around behind the grocery store and root through their dumpster, so take your pick.
Some people prefer to have a safety net tucked away somewhere, even if it's only $100 bucks, so that just in case something happens, they know it's there. I've never bothered, because chances are I would just spend it on something stupid anyway, then regret it a week later when I'm in a worse situation.
Like everyone's said above me, if you have a couple skills, doing anything, they will be enough to take you as far as you want. Don't just rely on money... that's about the worst thing you can do, in my opinion.