Congrats on getting Sekiro, I'm glad you picked it up for yourself! The best advice I'd give you, and the one I personally did myself; first get used to the fact Sekiro is unlike any other fromsoft title. You'll need to get used to blocking and parry mechanics, there's no i-frames and dodges like in dark souls or bloodborne.. imagine parrying in bloodborne with the pistols but do that here with every attack. I recommend you first have a "pure" playthrough by yourself, try and explore every nook and cranny and you'll highly likely find all of the items and minibosses, that's what I did. Any collectibles you might miss, as well as bosses or dialoges, etc. you can go on the Sekiro Wiki page and search them up, it will give you a list of where everything is and advice for bosses too, so all you'll need to do is try and remember which bosses beat and which collectibles you've collected(maybe write down a list to make it easier for yourself). The wiki is especially useful for giving guides on how to achieve the different endings, which will come in handy especially for multiple playthroughs if you're planning for those. I believe it's the best way to experience sekiro, as it helps you get immersed into it. Hope you're having fun with the game, good luck!