I’m under the impression that the days of cheap buffets and drinks went out with the mafia, what affordable or interesting things are worth doing in Vegas?
The food at the Golden Gate on Fremont Street is cheap and really good. $2.99 shrimp cocktails
You can get a reasonably priced selection of international Coca-Cola flavors at Coca-Cola World on the Strip, the last time I was there it was something like $7 for 16 flavors.
The Pinball Hall of Fame and the Neon Sign Museum are both interesting things to see. The lions are free to look at in the MGM Grand.
Drinks are free if you’re gambling.
I like to watch the fountains at the Bellagio, especially at night. No charge for that and quite a show!
Do the Red Rock Loop. Free, unless you get a speeding ticket!
Simply people-watching in Vegas is entertaining as hell. Fremont Street in particular is like an alternate universe. And I enjoy just walking around the casinos, especially the fancy ones like the Cosmopolitan and the Wynn.
The wildlife habitat at the Flamingo and the flower conservatory at the Bellagio are both free. The Bellagio fountains are a must, especially at night.
For what you get and how much you get there are still some really affordable buffets. There are also some cheap lower quality buffets.
Food? IDK, I don’t mind the buffet prices. But, Every casino (I think?) has a free lounge where you can sit and nurse a beer and just hang out.
Bet $10 on a baseball game and spend three hours seeing if you win.
I second Red Rock Canyon. Beautiful to see or hike at.
Go to old downtown Las Vegas. The food and gambling are both cheaper there.
This. Grab a beer at one of the outdoor bars (I like Binion’s), and just watch the people go by. Better than TV.
I once spent a day in Vegas where the only thing I ate was the olives in my free bloody Mary’s! Dirt cheap meal if you plan on gambling and are a bit of an alcoholic anyways.
One thing about going to old downtown (Fremont Street) is the free overhead light show.
Fremont street is so much better than the main strip. Soo much better for so many reasons.
If you are interested in the history of the atomic bomb, there is the The National Atomic Testing Museum.. The have a lot of artifacts from atomic tests.
Speaking of museums, check out the Clarke County Museum, lots of history about the founding of Las Vegas and the building of Hoover Dam. It’s a short drive to Henderson from Las Vegas.
Several hotels on the strip have free shows. The Bellagio fountains have been mentioned, but the Mirage has a “volcano,” and Treasure Island has a pirate attack. Note that all these are less than ten minutes each.
There’s a half-price ticket booth on the strip if you are interested in seeing a show.
This, and drive through Death Valley, go visit Lake Mead if it hasn’t all been used up yet, visit China Ranch Date Farm, visit Mountain Springs Saloon on the way to Pahrump (I think that’s the one; only judging via Google Maps), make sure you visit Bonnie Springs Ranch while on the Red Rock run, and go visit Area 51.
Obviously you will have need for a car.
That is a helluva lot of miles on long lonely desert roads. Better stock up on Red Bull and good drivin’ music before you go. 
And it’s still better than going into Las Vegas or to the Strip!
There’s no “e” in “Clark County”.
Not any more, sorry. Took it out at the end of 2013.
I first tried In-N-Out in Vegas. It’s pretty cheap. 
Also, downtown there are lots of places with cheap food. And gambling can be cheap. Sit at a bar, plug the occasional dollar in the video poker machine, drink for free and watch a ballgame.
Also, I much preferred downtown to the strip. Downtown is cheap and cheesy, with neon signs and $2 breakfast buffets and quarter roulette. The strip is all LEDs and fancy palaces and rich people in evening gowns and $20 table games and $100 stage shows.