I agree that the most important thing is not an endless spreadsheet with the best ever price on anything you ever buy, it's setting a reasonable budget, and then periodically challenging yourself to go lower as you get to know your habits. Starting with prices on your staples is a good. You can also consider what foods are the most expensive ones in your diet, and focus on getting the best deals on those first. It might be meat, organic yogurt, whatever. For us it turned out to be nuts! :) A couple of pounds of nuts that lasts us a few weeks could be $18-20 here!
Remember, too, that refining your grocery budget is a multifaceted process that will go through many stages. For now, just looking through the grocery flyers and getting to know what the sale cycles are is a good base. If you randomly see an amazing deal, stock up. For example, the breakfast cereal we like ranges across supermarkets from 9-$11/kilo. We know that it periodically goes on sale for $7, and sometimes as low as $6. When it's $6, we stock up. If we start to run low, though, we just look for the next sale. If that's $7-8, we go ahead and buy a few more bags. We're not trying to buy a year's supply at THE best rate. But we do recognize that best rate now when we see it.
But that's just phase 1. Over time (don't put pressure on yourself; as you master your basics, you'll know when you feel ready to tackle this budget again). If you read around the grocery bill forum threads, you'll see that people try a variety of strategies. Instead of just getting the best price on a turkey, maybe they wonder if they actually NEED turkey; maybe chicken, which costs less, is ok to eat more often. Or maybe that expensive staple (nuts! :) ) doesn't need to be a staple at all; maybe we could eat hard boiled eggs instead for a high-protein snack. Maybe we just focus on wasting less and shopping less often, learning to make soup out of the leftovers and bread pudding out of the stale bread. Maybe you feel ready to start baking your own bread, or making your own yogurt! There are lots of ways to meet a budget. But if you are among the fortunate few who get to do this by choice, instead of because of necessity, then go easy on yourself, keep the big picture in mind, and be patient.
(Just as an example, I love food, and going grocery shopping used to be one of my husband and my favorite dates on a Saturday night! Yup. We were that geeky. Today, more than 15 years later, we do so much of our own food producing, food processing, bulk buying from local producers, foraging and bartering, that we hardly buy anything at the grocery store at all! You just never know where these journeys might take you. )