Bags might just be the most useful and important accessory to a mom, I think, especially city moms who don't have cars. Personally, I spend most of my life walking around town with various bags filled with stuff, from groceries to dog food, library books to ice skates and baby wipes. Some items all moms need to carry, always, like a wallet and ID, a phone, inhalers or epi-pens or other emergency medicine, and if you're like me, emergency sweet treats too. Between all that and your keys, and pushing strollers or carrying / dragging your kids and pets and gear like bikes or scooters around, all hands are full to the max all the time. And this is where the importance of THE BAG really comes in. Without the right bags, a mom is lost.
I have found that having several different kinds and sizes of bags at your disposal at all times is hugely helpful. I always have several very large, very study, cheap bags by our front door, in my bike basket, and even in my car. I use these almost daily for grocery shopping (this saves time and the environment, in a huge way), and for lugging around larger and / or heavier items like books, groceries and kid's gear like soccer balls or sand toys. These bag are also great for picnics and BBQs, beach days and so much more. I love the Ikea ones for $0.59 here http://www.ikea.com/us/en/catalog/products/17228340/
And the nicer looking ones I got for very cheap at the checkout counters at Home Goods and Whole Foods. They last forever!
As far as personal purses or bags, the ones we ALWAYS need, with our wallets and keys, I find that a small one that just holds the essentials and has a long strap works really well, like any of these great "mini bags" from LeSportSac https://www.lesportsac.com/style/mini-bags which come in so many shapes and really cool patterns and amazingly durable fabrics (including slivery faux snake skin!) Many moms I know also love their "bucket bags" like these http://www1.macys.com/shop/search?keyword=bucket+bag, which can hold a whole lot, like a bucket, but looks way more stylish. These work best if you keep your important items organized like on a key chain or snacks in a large clear Ziploc, or in designated, pretty and reusable food saver bags like these LunchSkins http://www.amazon.com/LunchSkins-Reusable-Sandwich-Snack-Bags/dp/B004K1SR9Q/ref=sr_1_6?ie=UTF8&qid=1390752963&sr=8-6&keywords=fabric+food+storage+bags, so they don't get lost in the mess of the bucket.
What kind of bags do you think are best for busy moms?