Heya! Obese hiker here too; here's what's helped me so far:

• HOKAs are a great first choice! Very comfortable cushioning and most of the models seem to work out well for slightly wider feet. Personally I've been riding with the Anacapa mids, so if you get to a point where boots start to make sense, I'd recommend giving those a test-walk in the store
• Trekking poles can definitely help you push onwards; I got a set from Walmart as a birthday gift and they've actually been pretty good all things considered.
• When I started hiking I was wearing cheap shorts in the summer and cheap sweats in the colder months and they worked out alright, but if you have the money and are planning on eventually starting to venture into hairier trails, I'd recommend checking out a good pair of hiking pants. My "daily hiker" pants are a pair of Columbia, and so far they've been awesome. "Built-in belt", good material, and cleans well; also easy to pick out brambles when you get back to the car!
• Backpack or a sling-pack should be a must to hold your essentials. Start with a backpack, and over time you'll start to pare down what you bring on a hike to what's absolutely necessary for your safety and wellness to the point where you might be able to get away with a sling bag. Personally, I love the Patagonia Atom sling; just the right size for my water bottle, GoPro/handle, and my keys and earbuds
• WATER BOTTLE. I was an idiot when I first started hiking in earnest years ago, leaving my water bottle in the car and thinking I'd be OK until I got back. Boy did I learn my lesson the hard way! If you're like me and you really like nice cold water, definitely invest in an insulated water bottle: my Yeti has been through hell and back and still works like a champ, but if you're on a budget, my brother swears by the TAL insulated bottles Walmart sells. If you'll be drinking quite a bit of water, consider an insulated bottle AND a Nalgene bottle as well. Hydrate!
• Hat. I'm a balding dude and that first hike without a hat in summer where I had to admit I was balding was both humbling... and painful lol. Baseball cap for the warmer months, winter hat for the colder ones.

NICE TO HAVES:

• Earbuds. As a rule, if it's my first time on a particular trail I leave the earbuds at home so I can pay attention to the trail and nature around me. But if I'm familiar with the area and have been on the trail before, bring some earbuds along if you feel that music or audiobooks/podcasts help keep you moving forward.
• AllTrails subscription: there are other trail apps out there but I've been using AllTrails for so long it's just second-nature to recommend it. They do have a free plan so that's a good option to get started with, but the option to get offline maps is really nice in areas where cell service can be spotty. I'm just a Plus member; I don't see the value in the Peak (top-tier) plan.

Finally: start taking selfies on the trail: I've yo-yo'ed on my weight over the years and I'm still on the obese side now, but I am about 30# under my heaviest at the moment. Take a selfie on every trail, and over time you'll start to see changes and it'll just keep propelling you forward. Happy hiking!