I almost exclusively play reels.
In your typical bet range, I'd look for the following types. My pictures may show higher denominations/bets but they're available and/or playable at lower denominations.
-----3 reel 5 line quarter slots, max bet would be $1.25. Triple Double Diamond is a good one. Better are the kind like Triple Red Hot 7s or 3x4x5x that pay something on the special symbols.
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-----20 line 3 reels with free games. They're usually penny machines with a $2 max bet.
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-----Pink Diamond Free Games in 25 line. I was just in Vegas and Bellagio and Cosmo have these. CP has the 5 credit 10 line type. While I will play the 10 line, 25 line is better as you get something on almost every spin. The 25 line you can find in pennies, max bet $2.50. Max bet only matters for the 3 triple pinks. On my picture I have the multi denom cranked up to nickels and am max betting - only time in all my play on these at various places that I got the 3 triples. One of the few machines that I go over $5 a spin.
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-----Sizzling 7s in 25 cent denomination. I max bet 75 cents on these but you can play just 50 cents and the 7s will still count. In my experience if you're going to get 7s you will get them fairly quickly, so these aren't typically machines I settle in to play for a while. I've gotten mixed sevens or 3 red sevens a lot on the 25 cent ones but I don't have any pictures. If I'm doing well at a place that has it I will throw $100 in a $5 denom one for 10 spins at 2 credits each and at least 50% of the times I've tried this I've gotten 3 red or 3 mixed for a quick payoff. Never gotten the three Sizzling Sevens on any denom.
-----Multi line 5 reels. The more lines the better. I like the one Dvandentop posted videos of but that one can run hot or cold. There's also Double Gold, Triple Strike, etc.. There are the types like the ones in his video that have bigger symbols. There are also ones that have 5 reels of smaller symbols....Triple Sevens, Triple Red Hot 7s. The smaller symbol ones come, in my experience, in 9 line or 20 line. 20 line is better. Max bet varies but it only matters for the top paying symbol set. My picture is at max bet and is one of my better hits on these but I've gotten lucrative combinations at bets per line below max bet.
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-----One line 3 reel slots, where the only up for playing max credits is for the highest payoff, and where there's some multiplier or special symbol that pays by itself if it lands on the line. So slots like Triple Diamond, Triple Stars (or Triple Double Stars), 3x4x5x Double Times Pay, Triple Red Hot 7s. These can also be good in quarters at max bet of 50 or 75 cents. In your bet range this would be $2 at one credit, $1 at one or two credits, and down to 50 cents or 25 cents. On the <$1 slots I would play max credits.
-----$1 Quick Hit, 3 reel one line, max bet $2. The kind where you get paid for the Quick Hits symbols whether they're on the line or not. They usually have a progressive for the 3 scattered Quick Hits that starts at $1000. The pic below is a win I got on one of those. The three Quick Hits in a line that is on my profile picture was on the non-progressive type that always pays $1000 for 3 scattered and does not have an accumulating progressive attached to it.
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-----4 reel one line slots in quarter denomination at max bet, usually 75 cents. Triple Strike, Triple Hot Ice, etc.. They can run cold but when they are paying they are good for a lot of smaller hits with the occasional larger one that can get you a lot of play for your money if not a profit depending on when you walk away.
At a casino (not VLT) I usually go with 20 spins as that has worked well for me. In the case of a $5 reel I'll put $100 in and spin it through. I've seen bigger hits come through in those later spins after nothing for the first dozen more often than I haven't that it's been worth my gamble to do that. In the case of $1 reels with $3 max bet I'll put in a $20 to start and see where it takes me, but never more than 2 more and sometimes not even that. On other bet levels I don't put in more than one $20, unless it's a machine I know as in I have played that particular machine at that particular casino before.
With the multi line machines you can get nice individual hits, like in my picture and on dvandentops video, but for the most part you will get a lot of small and medium hits that will keep you hovering around the amount you originally put in until the machine eventually goes cold and quits paying anything. So it's always a judgement/gut call as to when to cash out with the original money or thereabouts. I love them because your money lasts and you can rack up tons of coin in.