The good news is that it doesn't really matter which game you play first because there isn't a particularly continuous story between each one. There's a development of themes, to be sure, and references to the previous games in the series dotted around, but you won't miss too much. They're in chronological order but there is, to be purposefully vague, a focus on the idea of endlessly repeating cycles, so that doesn't overly matter.
DS1 is a kinda rough game to be your first game because, despite the sense of superiority its fans give it over the other titles, it does have some flaws that are rectified by the later games. Performance issues in some areas, wildly broken metas in multiplayer (though later titles never fundamentally address this issue, only bandage some parts), and in my experience, it's quite easy to get lost or wonder what you're meant to do next, especially if you don't have great memory or don't note down the location of every locked door you find. But that is counterbalanced by the "non-linearity" of the environment, at least in the sense that you theoretically have a lot of choice in where you can go. In practice, the enemies just being too strong in certain areas that you can access from almost the beginning limits you a great deal, but even so. Start here if you want to have a more complete understanding of the lore and are fine with a fair amount of challenge in exploration and navigating the world, and like having lots of ways to go.
DS2 is a black sheep as it was developed by a different group of people, and so while it receives a lot of criticism online, I think that's mellowed out over time. I only actually finished it a year or so ago and I really enjoyed it. It's actually probably the least linear game in the series on a technicality, but that won't matter to you. It certainly has its flaws, including a... controversial rolling i-frame system, but it's also the most... goofy? game in the series, at least for me. Still has the dark and gritty atmosphere and all that but it's also got comically large swords and weird armor sets. It also allows you to warp between bonfires right from the beginning, that is, checkpoints, which massively simplifies world exploration. Start here if you want a slightly more modern experience than DS1 and want to use swords that look impossible to even hold, and don't mind a bit of floatiness and jankiness every now and then.
DS3 is, as you might imagine, a more modernized Dark Souls game and developed by the same people that made DS1. It's really got a combination of things from both of its predecessors - there's a lot more references to DS1 than in DS2, but also has e.g. the ability to warp between bonfires from the beginning, which is super convenient. It's seen as quite non-linear, and that is to some extent true - it has some arbitrary roadblocks set up in some areas and it's very likely that you'll go down the same paths at the same times as other players, with only a few real crossroads. But I still think it's got a good balance of having a choice between where to go, and a progression path that is fairly clear to follow. It's my favourite of the three games and while every Souls games has awesome DLC, I think the DS3 DLC, in combination, are at or near the very top in my opinion. Start here if you want a more modernized experience with better graphics and QoL, and don't mind not being able to go down every path for as long as you can survive it without roadblocks.
The most important thing to know about Dark Souls 2 going in is that the Adaptability trait controls how many i-frames you get when rolling and you need to at least hit the first break-point at 12 points of adaptability to get 11 i-frames on your roll.
The good news is that it doesn't really matter which game you play first because there isn't a particularly continuous story between each one. There's a development of themes, to be sure, and references to the previous games in the series dotted around, but you won't miss too much. They're in chronological order but there is, to be purposefully vague, a focus on the idea of endlessly repeating cycles, so that doesn't overly matter.
DS1 is a kinda rough game to be your first game because, despite the sense of superiority its fans give it over the other titles, it does have some flaws that are rectified by the later games. Performance issues in some areas, wildly broken metas in multiplayer (though later titles never fundamentally address this issue, only bandage some parts), and in my experience, it's quite easy to get lost or wonder what you're meant to do next, especially if you don't have great memory or don't note down the location of every locked door you find. But that is counterbalanced by the "non-linearity" of the environment, at least in the sense that you theoretically have a lot of choice in where you can go. In practice, the enemies just being too strong in certain areas that you can access from almost the beginning limits you a great deal, but even so. Start here if you want to have a more complete understanding of the lore and are fine with a fair amount of challenge in exploration and navigating the world, and like having lots of ways to go.
DS2 is a black sheep as it was developed by a different group of people, and so while it receives a lot of criticism online, I think that's mellowed out over time. I only actually finished it a year or so ago and I really enjoyed it. It's actually probably the least linear game in the series on a technicality, but that won't matter to you. It certainly has its flaws, including a... controversial rolling i-frame system, but it's also the most... goofy? game in the series, at least for me. Still has the dark and gritty atmosphere and all that but it's also got comically large swords and weird armor sets. It also allows you to warp between bonfires right from the beginning, that is, checkpoints, which massively simplifies world exploration. Start here if you want a slightly more modern experience than DS1 and want to use swords that look impossible to even hold, and don't mind a bit of floatiness and jankiness every now and then.
DS3 is, as you might imagine, a more modernized Dark Souls game and developed by the same people that made DS1. It's really got a combination of things from both of its predecessors - there's a lot more references to DS1 than in DS2, but also has e.g. the ability to warp between bonfires from the beginning, which is super convenient. It's seen as quite non-linear, and that is to some extent true - it has some arbitrary roadblocks set up in some areas and it's very likely that you'll go down the same paths at the same times as other players, with only a few real crossroads. But I still think it's got a good balance of having a choice between where to go, and a progression path that is fairly clear to follow. It's my favourite of the three games and while every Souls games has awesome DLC, I think the DS3 DLC, in combination, are at or near the very top in my opinion. Start here if you want a more modernized experience with better graphics and QoL, and don't mind not being able to go down every path for as long as you can survive it without roadblocks.
The most important thing to know about Dark Souls 2 going in is that the Adaptability trait controls how many i-frames you get when rolling and you need to at least hit the first break-point at 12 points of adaptability to get 11 i-frames on your roll.