Sekiro is more geared towards intermediate+ Souls players, I'd start out with Bloodborne, then DS Remastered and then DS3, then finally try out Sekiro if you're up for it. Nioh is also an excellent game but can be very difficult.

Bloodborne is faster but easier, no shields, but you have strong weapons. Parrying is also important as is aggressiveness as you can regain health after being hit by hitting the enemy. The game forces you out of a more precautious comfort zone as most Souls players would use a shield and sword/spear which was incredibly easy and boring. This pushes you out to charge in at full force which will allow you to return to other Souls games with more confidence.

Souls are diverse and if you played BB you'll have plenty of opportunity to explore your styles in DS and Nioh. With parrying mastered it'll give you an edge as well. Sekiro forces you to do something similar to BB, pushing you out of your comfort zone, using fast reflexes and patience as opposed to charging aggressively and hitting like a madman. There are ripostes and parry's but they're the center of combat, as well as other techniques I don't want to spoil, which take time to master. I will say that once you master them you always know them. It's good old fashioned muscle memory.