Your batteries for your camera:
1. you might want to use the silver (higher power) batteries for your camera (not Duracell), they are more expensive but they store, release and manage power much more effectively and are specifically for media devices;
2. Duracell aren’t good batteries at all… they leak their electrolyte (if forgotten or left too long) frequently (I stopped buying them because of that); and
3. check out the rechargeables that Costco sells.
The only problem with rechargeables is that they tend to fade quickly without much warning, unlike standard non-rechargeables. So what I used to do: carry an extra set of charged batteries, plus a set of non-rechargeables just in case I ran out.
And, for the most part, flash usage is not-necessary… it leads to overly exposed areas in front and darkness behind… Avoid using your flash as much as possible, just learn how to shoot without it! That’s it!