Sleep downtown, not on the Strip
The El Cortez on Fremont has rooms from $39 midweek and no resort fee, which alone saves you $45 a night versus the Strip. The Golden Gate and Plaza sit within two blocks and run similar rates. Downtown is walkable, has cheaper drinks ($4 beers at Atomic Liquors), and the Deuce bus to the Strip runs 24 hours for $6 one-way or $8 for a 24-hour pass.
Day 1: Fremont and free casinos
Walk Fremont Street end to end. The Viva Vision canopy show runs hourly from 6pm and is free. Play $5 blackjack at the D or Circa's Legacy Club; both keep low-limit tables all day. Lunch at the Heart Attack Grill (single burger $6) or a $2.99 shrimp cocktail at Golden Gate, a Vegas tradition since 1959. Dinner at Pizza Rock, $18 for a huge slice and a beer.
Day 2: Strip on foot
Deuce bus to the Bellagio fountains, then walk south. Free attractions: the Conservatory, Aria's fine art collection, the Venetian's canals (looking is free, gondolas are $34), the Flamingo wildlife habitat, and the Mirage volcano. Lunch at the food court in Miracle Mile Shops, around $12. Ride the free Aria-Bellagio-Vdara tram to save your feet.
Evenings: 2-for-1 happy hour margaritas at Cabo Wabo on the Strip until 7pm, $8 each.
Day 3: Red Rock on a shoestring
The RTC bus does not reach Red Rock, so split a rideshare with your hostel bunkmates (roughly $45 each way) or book the ShowStopper $65 half-day tour, which includes park fees and photo stops. If you have a car, the $20 entry covers everyone in the vehicle. Pack sandwiches from the Fremont Street 7-Eleven for $8 and drink 3 liters of water per person.
Good to know
How cheap can Vegas actually be?+
Sub-$400 for 3 days is realistic: $120 lodging, $60 food, $60 transport, $50 park, $100 gambling and drinks. Skip clubs and buffets and the number holds.
Is downtown Las Vegas safe at night?+
Fremont Street itself is patrolled and busy until 2am. Two blocks off Fremont, especially north or east, gets rough fast. Do not walk to Circus Circus.
Are there free shows on the Strip?+
Yes: Bellagio fountains, Mirage volcano (at press time under renovation, check status), Fremont's Viva Vision canopy, and the sirens outside Treasure Island have been retired.
Can I use the monorail on a budget trip?+
The Strip monorail is $5 a ride or $15 a day, and only serves the east side from MGM to Sahara. The Deuce bus is cheaper and covers Fremont too.