Stand directly behind the bike & check if the derailleur hanger is bent. A misaligned derailleur will cause chain noise such as you're having. A derailleur alignment tool will give the most accurate straightening, but you can do it reasonably well & easily just by hand. Shift the derailleur to the middle of the cassette, and firmly grasp the body of the derailleur (not the lower bit with the jockey wheels, 'cos you'll bend it). Gently use the derailleur as a handle to bend the hanger out until the chain is in line below the gear it's on. When you're happy, shift out to top gear, disconnect the cable & reset your limits.
Start with the high gear (outermost sprocket) limit: Wind the screw marked "H", which by nice coincidence is the upper of the two screws on the derailleur, in until you hear the chain begin rattling against the next sprocket. Then very carefully wind the screw back out just until the noise stops. Turn the cranks over & push the derailleur so it shifts up to the next sprocket, then let it go. If the chain hesitates on the shift, wind the limit screw out a poofteenth of a turn & repeat the test until it drops smoothly to the top gear. When you're happy, set the inner limit.
Still with the cable disconnected, push the derailleur by hand up to the big sprocket while turning the cranks over. If it overshifts & rides over or off the sprocket, wind the "L" screw in until the chain stays meshed on the gear. If the last shift is rough, wind the screw out to allow the derailleur to move onto the gear smoothly.
Let the derailleur drop out to the top gear again, and connect the cable. I've found that the 7900/6700/5700 family needs a fair bit more tension than the previous generation, so I grab the tail of the cable with pliers to get a bit more grip to pull some tension in the cable. With your cable under tension, clamp it down, ensuring the little hook tab on the clamp washer is pointing up, parallel to the cable, NOT clamped over it! Placing the tab over the cable causes the cable to kink & increase tension as the derailleur shifts inboard, causing it to pull too far & overshift. With the cable secured, run through the gears & fine tune with the barrel adjuster - wind it out (anticlockwise) a bit at a time if it needs encouragement to climb the cassette, wind it back in if it doesn't drop smoothly.
Just ride the bloody thing and enjoy yourself!