this is just a quick basic guide that works well for nocturne (works very well for me) and depending if you go good early and mid game you will become high ad/as/cr by late game. i also pologies in advance for any mistakes made

start with boots of speed and turn them into beserker greaves then start ionic spark with recurve bow then complete after this build ad/ls with bloodthirster starting with vampyric scepter and then bf sword next more as/cr with phantom dancer you should have enough by the time you return to base if not start with critical brawler gloves or cloak of agility. by the time you have these it will be mid-late game get your infinity blade for more crit and crit damage. if the game hasnt ended get another infinity blade for more ad/cr

you will need both heal and clarity for early-mid game dominance and when ganked/2v1 situations heal will give you that extra health boost for escaping or finishing that kill you need and clarity for more duskbringers for kills or getting away when you run out of mana.

start the game by buying boots of speed and head bottom or top (top if top right corner start...bot if bottom left start) start by last hitting creeps for 570 gold to finish berserker greaves. try and snag a early kill with duskbringer 1st and depending if your enemies are heavy spell user get shroud of darkness or if not get unspeakable horror for more hits before they reach the tower. go with a stun hero or volibear/singed due to their fling ability giving you the advantage to use unspeakable horror and snag a kill. by the time your lvl 6 you will have all abilities at least lvl 1 go for duskbringer lvl 3 shroud lvl 1 horror lvl 1 and paranoia lvl 1 and you should have ionic spark/berserker greaves and be working on blood thirster. try and push all 1st towers for the bonus gold and try for a few ganks and kills. at lvl 11 you should be working on phantom dancer with a few kills if you havnt killed dragon do it now you need the gold and try to push the 1st or second towers if you havnt already. when you get your phantom dancer start infinity blade starting with cloak of agility then b.f.sword. when your 1st infinity blade is done go for a 2nd but it should be late game by now if its still mid-late check barrons health if its 8-9k and you have infinity blade attempt solo or have a high health character attack 1st to take damage. when you have barroned push to win with your 800-900 crit damage high attack speed nocturne.