I have three bottle cages...two in the front triangle, and one under the down tube. (My frame pump sits on top of the top tube.)
I have an expandable wedge bag under the back of the saddle.
For long rides, I sometimes use a bento box on the top tube, and I sometimes rig a tiny little wedge bag underneath my aero bars, under the stem, in which I put my repair kit. That makes it easy to carry some extra clothes in my under-saddle bag, and it makes it easy to know where stuff is when it is compartmentalized.
I have a camelback, but I don't care for sweating against it. I really hardly ever truly need the 3 bottles, but I sometimes I have been glad for them, especially when I get a flat out in the middle of nowhere on a hot day.
"The best rides are the ones where you bite off much more than you can chew, and live through it." ~ Doug Bradbury