hiking: I just do light hiking, and all I need is a couple of sandwiches, a backpack and my boots. And plenty of water. Plenty of hills/mountains around helps, that's true
biking/rollerscating: you can get a decent used bike for about $100
picnic: just the food, and you need to eat anyway
board games: unless you need to switch the game every week I'd say you're covered with about $50 per year. We mainly play Settlers of Catan and Chess
lan party: I guess it depends on the games, we don't do this much anymore, but we're pretty old school when we do (CS, Starcraft 1, Worms World Party)
There's probably lots of other activities like that, for example we play soccer/foot tennis on a public field, and all it costs us is the price of the ball
Hiking: Buy boots and suitable clothes. Fuel to get to suitable location.
Biking/Rollerskating: Buy equipment. Fuel to get to suitable location.
Picnic: transportation supplies. Fuel to get to suitable location.
Board games: Expensive. Fuel to get to suitable location.
Lan party: Buy games. Fuel to get to suitable location.
All it costs is fuel, utilities, rent, and food. For someone with no income, that is all I can spend money on, and it has to be justifiable. Not "Oh, I play board games every once in a while", because I don't want to have to pass up on a job interview because I stupidly spent my transportation money on board games. Or whatever else.
Picnics, games, sports, lan parties, we just do them at home or on the public domain
hiking and other stuff needs some transportation, we either go with public transport or carpooling
I'm not saying I understand your situation, just that you don't necessarily need to spend a lot of money (or any) to have some fun with friends.