most Slot players has big bankroll to play because the minimum bet for most slots cant be considered as low for poor. Poor man's favorite game is lottery imho.
Lot's of games only cost $0.4 (minimum) per spin mate.
Yap, know about it very well. Even there are some slots with lower minimum bet than that. Probably $0.4 per spin is not that big for you but it can be something big for poor. I do believe poor will prefer to spend $0.4 btc for lottery instead of playing slot games. All in all, it is big or small is about preferences and depends on our pocket condition

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But with smaller slots you get better chances of winning, which does mean that you can have higher chances of winning if you are going to use a limited amount of cash.
At the same time it depends on everyone's personal experience. The same time it would depend on the casino you are following.
I had bad run on slot games lately especially with Fruit Party 2 as I did not get any FS after more than 5 hundred spins, I think it is my worst experience with Pragmatic slot.
I think I should stop playing slot games for a while and back to my other favorite game Crazy Ball aka Plinko.
I think you pick the wrong slots to play the "long game." That's the "problem" for high volatility slots because the longer it takes to bounce back (big win). You can down a lot before getting big wins. Thus, you need massive budget like what roycilik did.
Try medium volatility one if you play casually since it successfully brought my sanity back.
To be frank, I do not really care about the volatility of the slot games I like to play

As long as I like it (because of some reasons such as the UI or its feature), I'll play it as much as I wish but I will stop if I get no good wins after few hundreds spins.
Coming up to budget, I have limited budget unlike roycilik. I'll say $50 per session and I usually use it to play 1-2 slot game only.
1-2 slots? For 50$?? This is honestly a lot, I would rather take small sessions since I did hear once that your probability of Winning in the penny slots is much more as compared to the normal ones. Therefore you might as well try and split them up more.