Borys, if you have your route mapped out, I highly recommend using Hotwire. You can find three star and four star hotels for around $60 (sometimes less) in a lot of places. That's how I kept my accommodations affordable without worrying about roaches, crime, etc.
Great Rumbler's template is not a bad one, but gas is the killer. I would also make sure you have AAA or some kind of road-side assistance (I guess that's included with a car rental?).
This was what I drove the past month, approximately 3,000 miles:

And I spent about $1,000 and most of my expenses were paid for - including all of my gas and hotel up the Northeast.