Sore feet often end a first hike before fitness does. A blister forms from rubbing, and it can end the walk and the next few days with it. A first hike is mostly a test of your shoes and socks.
Your first day
Pick a flat, well-marked loop or out-and-back trail under three kilometres in total, and check it on a map app beforehand. Wear shoes with real tread, not flat-soled sneakers, and socks that aren't cotton, and bring water, a charged phone and a small roll of blister tape. Check the weather and sunset time, and tell someone where you're going and when you'll be back. Walk the whole thing without rushing, paying attention to how your feet feel the entire way.
Most people ignore a hot spot on their foot because it doesn't hurt yet. Don't. That faint rubbing feeling, left alone for even another kilometre, becomes a blister that ruins the rest of the walk and sometimes the next few days too. Stop and tape it at the first sign.
The thing most people miss
Distance and steepness get the attention, but for a first hike the footwear decides how it goes. Cotton holds sweat against the skin, and wet skin rubs. Wool or synthetic socks move moisture away, which is what stops the rubbing, and shoes with real tread grip wet ground where flat-soled sneakers slide.
Both cost little and neither depends on fitness, so choosing socks and shoe fit before choosing the trail is choosing the equipment that will actually decide how you feel at the end.
What not to buy
Don't buy trekking poles or a fancy pack before real tread. Shoes without grip are a common first mistake, and no amount of gear further down the list fixes shoes that were wrong from the start.
Once flat trails feel easy, pay attention to elevation gain, the total climb a trail includes. Two trails of the same length can differ hugely in effort, and elevation gain is the number that tells you which is which.