Considering your user name, you're well on your way! (If you're like me, you'll meet cyclists on the road who spent more on shoes and pedals than you probably spent on your whole bike.)
Ditto the suggestions about documenting where your money goes. I keep a small column in my journal for daily expenses.
Those expenses vary widely among cyclists. I had one warmshowers guest who had been living decently on his bike, just above the bum level, for about five years, riding about 8000 miles per year, on about $5000 per year. That works out to less than a penny per mile and that's incredibly cheap. Others require well over $50 per day! I'm a $25/day cyclist on long trips--about $10 on food, $10 average lodging (a motel every week, free camping otherwise), $5 misc like museums, bike and gear replacement/repair. It can be much cheaper if you cut out the motels and engage in a little "freeganism."
Free camping is widely available across much of the country (except where it isn't). Don't be afraid to ask. A smile and respectful attitude will open lots of doors.
Good luck on your trip and have great fun.