Group by expiry date, for sure - once they're past that, you'll just be putting them in the bin, so the point, surely, is to have them in date order so you know what must be eaten first, that's the priority, regardless of the product. That's the way products are stacked on supermarket shelves, with the shortest dated produce to the front, longer at the back. Admittedly, theirs are grouped by the product, then the date, but you've got, presumably, a random selection available, so in those circumstances, the date is the consideration.
As an aside, I'd also say don't buy so many snacks, that'd make life a lot easier (and healthier, probably). And don't shop when you're hungry, you'd be surprised how much easier it is to walk straight past snack type food and only buy what you need when you've got a full stomach.