A positive attitude.
After that, I would like everyone participating in a hike to come fully equipped, but I realize that is not practical, and it is more likely that a beginning hiker will accumulate the basic and emergency hiking equipment as they go along.
But there are some things that are so inexpensive and easy to obtain that no one should ever hike without them.
0. The phone number of the person you gave your plans and expected return time, who will call the proper authorities if you don’t return as expected. You don’t really need the phone number, but taking it helps you to remember to give that information to a trusted friend or family member.
1. A whistle. A “pealess” one is best, but any whistle is better than nothing.
2. A compass. A good quality compass is best, but a cheap dollar compass is better than none.
I have a dozen or so combined compass-whistle-waterproof-match-containers I can lend to those who might need one. They cost $2. You can find them at Walmart, Dicks, Gander Mountain, K-Mart, etc. The whistle has a pea but will work in a pinch, and the compass is sufficient to keep you headed in one direction.
3. A map. Even if all you do is print a black and white copy of the maps I post (select the “High Topo USA” option first.)
4. Water. You can survive 3 days without water. But the risks of heat stroke on hot days and hypothermia on cooler days is significantly increased by dehydration. Dehydration also increase the incidence of cramps and reduces mental acuity, which in turn increase the risk of injury.
5. Food. You can survive 3 weeks without food, but as with water, staying energized reduces the risk of other hazards.
6. An emergency shelter. A good start is either a $2 space blanket from Walmart or a larger space blanket from Dicks, EMS, or Gander Mountain for about $8. The next step up would be a $30 emergency bivy.
7. Rain gear. A good start is the 88-cent Walmart emergency poncho. At that price you can afford 2 of them.
8. Bug head net and bug spray (I like 100% Deet), also available from Walmart for a couple of dollars
9. Head lamp or flashlight. Even a dollar store flashlight is better than none. A $10 headlamp putting out at least 30 lumens is better.
10. Basic first aid kit. Adhesive Bandages, sun screen, mole skin, and tweezers at a minimum.
11. Dry clothing – socks, top, and bottom.
There is a lot more you can add to to a survival kit, but those 12 items listed above will be enough to get you started and can be assembled for less than $10.
As for hiking clothing, you should avoid cotton because it holds water like a sponge, increasing the risk of hypothermia in cool weather and weighing a ton in hot humid weather. Nothing says “I’ve never hiked before” like a pair of blue jeans.
Footwear is a tough subject. Any thing from barefoot (yes, there is a barefoot hiker movement) to high end backpacking boots. In warmer weather, sneakers are OK to start but are not the best for plowing through mud or crossing creeks (all the more reason to have a dry pair or two of socks.) Most casual hikers will do just fine with a pair of $30 or so hiking boots from Walmart that fit their feet well. Crocs and sandals are about the only thing prohibited because they increase the the risk of the hike being disrupted by an injury to a participant.
In winter, warm waterproof footwear is more critical.
There are some winter hikes where snowshoes or supplemental foot traction (micro spikes, STABILicers, or other over the shoes ice spikes) will be needed. that requirement will be stated in the hike description when it applies.