If you were to ask this question on an online diving forum such as ScubaBoard, which has a snorkelling section, you might get thirty different answers. Most of the answers would simply describe why the poster's own gear is the best in the world because it matches the poster's own expectations, not anybody else's. So my advice is to forget about brands and models, focusing instead on equipment that fits and suits you and your girlfriend. And don't just opt for a snorkelling "set" or "kit", whose only advantage is that each item will be colour co-ordinated.
Start with the two snorkelling essentials: a mask and snorkel. The most important criterion in mask choice is fit. A leaky mask isn't normally life-threatening when snorkelling, but it can be a major irritation. Facial dimensions vary and one mask definitely does not fit all. Go to a reputable dive or sporting goods store and try out the masks for size by pressing the inside of the mask against your face, breathing in slightly through your nose to create a partial vacuum and without attaching the strap. If the mask stays in place without support, then you may have a suitable candidate. Make sure that the mask has a comfortable skirt, made from soft silicone or rubber, with a "feathered edge" that seals snugly against your face. Some snorkellers prefer "low volume" masks which can be cleared of residual water more easily. If you are planning to dive down several feet, make sure your mask has the wherewithal for you to pinch your nose so that you can clear your ears when submerging.
As for snorkels, some people prefer a simple "J"-shaped breathing tube with just a mouthpiece at the short end and with less to go wrong. Others swear by a "dry" or "semi-dry" snorkel which has a valve to exclude water from the snorkeller's mouth when submerging.
Fins aren't snorkelling essentials, but there is no doubt that the snorkelling experience is enhanced by their use. I once snorkelled at La Jolla Cove in Southern California, one of the world's best snorkelling venues, and observed how the snorkellers there were shod with every kind of fin imaginable: open-heel rubber bodyboarding fins with fixed straps, open-heel scuba fins with adjustable straps and plastic blades, open-heel Force Fins, closed-heel all-rubber swim training fins with standard blades and closed-heel freediving fins with extended blades. The only common factor was that everybody was having a wonderful time with their personal choice of fins. When choosing fins, start by finding a pair that fits. Fin foot pockets don't just fit length-wise - if you're a size 11, then a pair labelled "size 10-12" may be your size - but also width-wise and in terms of arch height. Perfectly fitting fins are a joy, but you have to look hard - at your local diving, swimming or sporting goods store or the online equivalent - to locate a pair that matches your foot dimensions, not anybody else's. Fins that are too tight may cause cramping, while those that are too loose may raise blisters or fall off in choppy waters. A snug fit is what you are looking for. Closed-heel fins are more comfortable than open-heel ones, particularly if you are planning to wear fins barefoot. If you intend to wear fin socks or booties, you will need to factor in the extra bulk when sizing your fins. As for fin blades, you need to be aware that fins aren't worn for speed but for power, manoeuvrability and endurance in the water. Stiff-bladed fins will afford more thrust but will tire you out more quickly. Avoid fins with blades that are too floppy. I would also recommend traditional before gimmicky designs:
http://www.swimclub.co.uk/forum/attachment.php?attachmentid=1371&d=1198788608
http://www.funswimshop.co.uk/ekmps/shops/seriouslyfun/images/speedo-glide-fins-9474-p.jpg
Both are made by the same company, but while I own a pair like the first, I wouldn't be seen dead in the second pair!
You aren't beginning with a blank slate. You have already sampled the snorkelling experience and the gear you used will have left you with some impressions about what worked and what didn't. You won't have to spend a lot of money to get gear that fits and suits you, but be prepared to spend a little time finding a mask and a pair of fins that match your dimensions. Don't be pressured into buying anything just because it's a well-known brand. Happy snorkelling!