You could spend 10 dollars or 10000 dollars. If you want to hike. Go Hike! Find out were the local trails are and head out.
Throw on a comfortable pair of shoes you don't mind getting dirty. Cargo pants or light backpack for a bottle of water and 2-3 quick snacks. Let someone know where your going stick to marked trails. Check the weather for rain, bring a rain coat if it's due. Grab a hat for cold weather and/or shade for your eyes.
If you have kids take them with you, my 6 year old regularly does 4 miles that's about his limit before he's dragging. Take a friend, take a dog. Take your time and just enjoy the outside.
You can get cheap gear or spend spend spend and not have a clue on what you need.
Cheap light tent + an old small pot from the kitchen change of socks, heavy shirt, for cold evenings and an old blanket. Bit of food what you would typically consider 2-3 servings and your good for an overnight hike. Of course you'll need a few more basics.
The first few times just set yourself up so worst comes to worst 1 hour in a rainstorm and you can be back in a car headed home to a warm shower.