I’d recommend getting a decent pair of boots. Nothing crazy, for day hikes or even light weekend trips you don’t need a heavy duty trekking boot. But a good comfortable boot will make your hikes much more enjoyable. A lot of people are going for lighter trail shoes these days but I still prefer a little bit higher boot that provides at least some ankle support. You never know when you’re going to step on a rock or in a hole or something and turn an ankle. A little bit of support goes a long way in preventing ankle sprains or even just helping to brace a splint in the event you need to hike out on an injury. Also, if you’re serious about making this a hobby, picking up a pair of boots now will give you plenty of time to break them in on shorter hikes. By the time you work up to longer hikes or even overnight treks, your boots will have formed to your feet and have flexed with your step plenty. Trust me, there’s nothing worse than getting a few miles into a multi day trek and feeling those tell tale hotspots.
As far as brands go, my current boots are Asolo and I love them. They’re the only boot I’ve ever owned that needed almost no break in time. They run a little narrow, but some models are better than others. My previous boots were Vasque GTXs. I bought them before a scout trip to Philmont in New Mexico back in 1998 and they only just wore out a little over a year ago. They got a hell of a lot of use and were actually still pretty good but the soles eventually just rotted out. I’d recommend them as well.
I’ve got friends who swear by merrel and others who insist L.L. Bean is the best. Your best bet is really to go to a good outdoor gear store (REI, EMS, etc…) and try on every boot they’ve got. Twice! Ask the people at the store, they’re usually pretty knowledgeable. If you can find someone there who’s close to your size and weight, ask them what they wear. When you find something that fits well, ask if you can test em out. EMS, and I think REI, have no problem with you buying a pair of boots, wearing them around for a few days and then returning them if you don’t like them. Just don’t go stomping around in the mud.
Ok, enough about boots. Other handy gear is water bottles or camel bak type things, a first aid kit, pocket knife, sunglasses, sunscreen, hat, and maybe a light rain jacket (I’m from New England, our weather changes frequently, quickly, and often without warning. Other areas of the country don’t have this problem so it might not be an issue). Other things I like to bring with me, especially on solos, is a notebook and pen/pencil, and sometimes my camera. I find I get a lot of inspiration when I’m out on the trail and like to write things down or take pictures.
You said you plan on bringing your dog (I think you also said fiance, I hope these aren’t interchangeable.;)) Do yourself and everyone else out hiking a favor and bring a leash. Those extending ones are great. I know a lot of people who take their dogs out hiking with them and as soon as they get away from the cars, let the dog off leash. This seems great, the dog gets exercise and can run around and sniff and piss and shit and do whatever it is that gets dogs off. Unfortunately dogs also get excited when other people, or dogs, or wildlife show up. Dogs can scare people, fight other dogs, and wreak havoc on wildlife. Lots of people go hiking to see birds and other wildlife. Even the animals that aren’t afraid of humans anymore will freak out at a barking dog. If you want your dog to run around and get some exercise, great, lots of hikes have fields, ponds, and other areas you can stop at and let your dog run wild. Just be considerate of other hikers and the environment. I’m not trying to sound like a dick or anti dog, just something a lot of people don’t think about but a lot of hikers and, more importantly, park rangers, get mad about.
Anyway, I’ve rambled on long enough. If you have any questions PM me. I’m sure you’ll enjoy your new hobby, there’s really nothing else on earth like getting out in the woods away from people and cars and buildings and whatnot.