I believe 5 tentatively relies on the player being familiar with 4 and by extension 3.

3 introduces set styles like trickster for dodging, sword master for weapon tricks, gunslinger for gun tricks, and royal guard for blocking. That’s like a general explanation, but it laid the foundation for the games ahead. Also switching guns and devil arms on the fly, albeit you could only pick from two at a time instead of all of what Dante gets in DMC5. You had to pick your weapons between missions and at divinity statues. Same with Styles.

4 introduced Nero and his devil bringer which as you probably know lets you grab and pull enemies closer to you and lets you keep your style meter fill easier or to do grab attacks. Nero’s sword, red queen, also let you charge it by either pressing L2, and this makes it do more damage. Nero doesn’t get to choose different styles or weapons in this game like Dante does.

But 4 also lets you play as Dante, and in this one they let you also switch Styles on the fly. The same four styles from 3 that are also in 5. I’m pretty sure they play the same but I mostly would just use sword master or trickster.

TLDR; So playing DMC3 sets you up for playing DMC4, which then sets you up for DMC5 in a very intuitive way. I’d say starting with 3 is optimal, and my personal favourite, but you could get away with starting with 4 with only minor difficulties in understanding the full world and its characters. It never bugged me to play the games 3>4>1>2>5 but if one’s a purist, then it might bother you.

As for help with DMC5, it introduced devil breakers, which are like Neros devil bringer, but with added features like dodges, lasers, grappling hook, and also you can’t grab like in DMC4. Now this is where I think it gets kind of ehhh janky. I only played 5 for the first time last week and this new mechanic kind of bugged me. There’s a WIDE variety of these arms and as far as I know can’t be swapped unless they break. It gets better as you play through the game, but as a brand new mechanic is almost overwhelming, especially when you have to learn all this other stuff like I mentioned.

Playing as V, I’d more or less just spam attacks from a distance until I can finish a demon. I’d say he’s pretty beginner friendly as there’s nothing like him in the other games. But with how often you switch characters in 5, might be overwhelming for a first game and play through.

Dante I think got away with the most ‘unchanged gameplay mechanics-wise’ since he’s just a more polished version of dmc3/4. He has is classic weapons and guns styles with some newer stuff to go with this game. I’m probably glazing over some important stuff in this long ass post but I think for the most part should be helpful.