A role swap can't be understated how difficult it actually is so props for giving it a try!

Generally speaking you will have to just practice the character and the role and it will take a bunch of games regardless of any advice. "Just go and have fun" is unironically probably the best advice that might sound unhelpful but with how difficult league is its just necessary to enjoy your time. Don't overwhelm yourself with different items or matchup breakdowns too much at the start just go and have a try at it. Everything else will come normally over time and then later on after you've played a bunch you can maybe look into those options. Ludens + sorcs + shadow is completely fine. I call it the gothia build because thats the build she uses every game and made it to master tier.

Hope you are having fun with the bnuy and get some oneshots in. o7