8/26 Update - Added Star Slots information
This is the "Casino Games" section of my Swagbuck Games post: To All The Swagbuck Games I've Ever Played.
If you are interested in other types of Swagbuck games, refer to the previous post for links to additional game groups. I had to break the original game post up because the word count was too long to add any more content. This post will be updated as I complete new Casino offers. I will update the first line of this post with a quick summary of changes when new information is posted.
The following is a list of the games discussed in this post. For those who are new to Discover offers or feel less comfortable with mobile games, in the following list I have marked easier offers with "(Beginner)". Items marked with "(Beginner+)" are on the easier side but with a bit more complexity. This is a standard marking I use across all my lists.
Here is a brief list of the games:

• Pop Slots (Beginner)
• Huuuge Casino
• Billionaire Casino
• Club Vegas
• Star Slots

Other items to note:

• I am an Android user. The offers below may only be available for Androids. I will note when they are for Android only when I see that in the disclaimer.
• I have not spent any money to complete any of the following games.
• I always recommend having accounts with multiple sites that have offer walls to compare offers. Here are some other sites that I have accounts at and have also done offers at:
  • GG2U (most recommended) (Ref | NonRef)
  • RewardXP (Ref | NonRef)
    • Full Disclosure: Have not used this site yet, but received a good recommendation from someone who has been using these sites for longer then me, saying they have some of the highest payouts they've seen. The company also reached out to me to inform me that they had a higher offer for War and Magic then I had commented in my guide. They have good offers, a good payout rate, PayPal and Amazon options, and low cashout minimum.

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Pop Slots ($25)

This was by far and away the easiest Swagbucks game I've played to date. I completed it in under 2 hours. I wrote up a tutorial here.
Time to Complete: Level 28 offer took me less then two hours and I wasn't completely passive. Level 35 offer (which I helped my sister-in-law with on a non-Swagbucks site) took me 2 days, but we just had the phone sitting on the counter while we did other stuff. Needed a restock on tokens the next day for the level 35 offer.
Credit Experience: Credited immediately without issue.
Biggest Con: None
Overall Recommendation: Would definitely recommend. I've seen the offer amount go from $25 down to $5 back up to $15, so I would say hold out for atleast a $10 offer.
Guide for Reference: [Guide] Pop Slots

Huuuge Casino ($20)

Another slots game like Pop Slots, but they also have some non-slot games like poker and roulette.
First off, I did not complete this offer. This was one of the first offers I did on Swagbucks and I didn't know how to really gauge if offers were doable or not, that offers have different completion times, etc. Unfortunately the offer I selected was a level 200 in 10 days offer. By day 6 I was at level 164 and low on chips. With how much I was having to bet on slots or roulette with each level, I knew there wasn't any hope without spending money at that point.
Fastforward a couple weeks later and I learned a tip that would have probably saved me: you can create a private roulette table! This significantly reduces the time each turn at roulette takes! In hopes of helping others looking at this offer, I wrote up some game tips that are probably good to look over before starting Huuuge. If I had known all these before I started, I would have definitely made it to level 200.
Today there was a post on the forum from someone who says they reached level 200 in 6 days after buying a $6.99 chip pack with 800+ million chips. They also commented that the roulette grind was rough, taking 15+ minutes per level. Otherwise their tips were the same as what I had posted.
Time to Complete: Did not reach level 200, but without making any purchases I would say don't take an offer that was less then two weeks. You can run the slots passively, but the non-slot games need interaction for each round/hand.
Credit Experience: n/a
Overall Recommendation: I would not recommend any level 200 offer unless it was not time constrained or if you were planning on making a purchase. There is usually also level 100 offer for less money (~$8). Give that an attempt on a double SB day.
Guide for Reference: [Guide] Huuuge Casino and Billionaire Casino

Billionaire Casino ($20)

8/26 Update: Swagbucks increased this offer to $50 for level 160 in 14 days. This is up from $20 level 150 offer that they had been running on and off for a while. It had jumped up to $40 for about a month before it jumped to $50.
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I honestly hate the Huuuge branded slot casinos. They just aren't fun to play and you need to be semi-active for the roulette grind. This offer was to get to level 150 in 14 days, so the grind was much less then the level 200 Huuuge Casino offer. Yuck! I had some good luck getting 2 Charm event packs completed for big chip wins so I was able to complete in 3 days, grinding roulette when I had the time. The offer went pending after maybe 10 minutes. (Note: the Charm event was a limited time event)
If you're planning on doing Billionaire Casino, my tips write-up for Huuuge Casino also applies as they are basically the same exact game: here.
Time to Complete: 3 days, but lucked out with some event chip wins
Credit Experience: Pended immediately
Biggest Con: The grind! It can kill your spirit and your soul, especially if you're unlucky with wins, events, or the lottery wheel.
Recommendation: I would only recommended level 150 offers or lower. Pended without any issues, so expecting to credit in the next couple days.
Guide for Reference: [Guide] Huuuge Casino and Billionaire Casino

Club Vegas ($12.50)

Another casino offer. There are times in the middle of these casino offers that I just wonder why I put myself through this. I was at this point with about 15 levels to go and only 5 million chips when I happened to stumble across my own personal gold mine! It was the slot Spartan Gold. I am usually one of the unluckiest people when it comes to casino games, but I would hit huge win after win after win with that slot, including two Grand jackpots, one valuing over 400 million! I honestly think that slot might be bugged.
Remember to collect free coins each day at a site like this one. When first starting the game, click offers starting with the most recent and going backwards until they stop crediting.
Time to Complete: About 3 days to reach level 70
Credit Experience: Pended immediately
Biggest Con: You can't put the game on auto. There are "spin" or "collect" screens that will just wait there forever for you. I couldn't find any slots that didn't have this. So you need to be able to check on the game every couple minutes.
Recommendation: The time limit was 30 days, so even without the crazy luck I had, I wasn't concerned about eventually getting there. I'm just bored out of my mind of casinos so its hard for me to recommend. If you like casino games and can babysit the game, then yes I would recommend.
Guide for Reference: No guide found....might need to write something up for this one...

Star Slots ($8.50)

I finished this offer a couple weeks ago, but wasn't able to write up a report on it until now so I'm trying to refresh my memory on this one. Thankfully I had a helpful commentor on the main thread who I'm referencing to jog my memory.
This is another casino by the Huuuge brand casino slots. It has similarities to Huuuge Casino and Billionaire Casino with two notable differences: (1) how clubs work and (2) no roulette table. Clubs do not have daily challenges (although they have a note saying they're coming). Instead clubs provide benefit by percentage increase of free chips as well as some free chips when members hit jackpots.
Remember to collect free coins each day at a site like this one. When first starting the game, click offers starting with the most recent and going backwards until they stop crediting.
Time to Complete: About 5 days to reach level 80. I wasn't focusing on it much over those 5 days so its possible it could have been doable in 4. A commentor on my main post added this about the recent level 110 offer on Swagbucks.

The 110 offer in 14 is definitely doable, but might be a bit tough without good luck. I got to 80 in about 6 days.

Credit Experience: N/A as I completed the offer on a non-Swagbucks site
Biggest Con: The slot machine minimum bet amount continues to increase as you level. Between that and the relative shortage of free chips, the likelihood of running out of chips increases. This just means you have to wait to replenish, but it does slow things down a bit. One hint is that the minimum bet amount only increases once you leave a slot and then start another one.
Recommendation: The level 80 one is easy to hit if you have 10-14 days. Be a little more cautious about a level 110 14 day offer. If you have 20+ days, I'd gauge that you'd have no problems either.
Guide for Reference: No guide found