I can tell you that in the last week of May, ten years ago, every time we walked by the bus stop in Sorrento for Positano/Amalfi, there were far more people in line than would fit on the NEXT bus, which was half-hourly. We never took the ferry to Amalfi. I do get the idea that ferries are believed to be a magic escape from a very overcrowded transportation system, but I just don't have the experience to know if that has any truth at all.
I'd feel better if we knew that you are sleeping in Sorrento before and after this day trip. That is, not coming from another place, or on a day stop of a cruise ship.
Do you understand that Ravello is hundreds of feet above sea level? After getting to Amalfi, you wait about 15 minutes for a bus to Ravello, which takes 10-15 minutes to go up there. (15 minutes is the average wait for a half-hourly bus ... ) One reason to focus on this is that there are not a lot of roads in this area. It's a long way from Ravello to Tramonti. It looks to me like (by bus) you have to go by way of Maori, which I believe has no ferries.
This is not complete research, and I don't think it's a real government website, but have a look at this bus chart:
https://www.ravello.com/sita-bus-schedule/
A problem with going to Tramonti second is that the bus through Maori (from Salerno, let's say) ends at Amalfi, where you take a second bus the rest of the way to Sorrento. That add a lot of latency to a very slow journey. I trust you already know that busses frequently get caught on sharp cliffside road turns and have to back up to make the turn, or get around some fools taking a picture from a car stopped in a travel lane!
Google Maps suggests that there is a smaller road that cuts off the descent to the coast, but that assumes you have a car and driver waiting for you:
https://maps.app.goo.gl/se3ukYqae2abWMfBA
Before you ask, this is an expensive transportation area, except for the cheap SITA busses. And you can't treat an imagined Uber ride like a trip home from a bar in a city of the USA. You have to "pay" for the vehicle's trip to pick you up, and for an empty return from a remote place. The taxi companies on the AC know what the traffic will bear, which tends to be 150 Euros (not actual research) for a trip from Sorrento to Amalfi. I don't know about adding on Ravello.
Clearly, you are on a budget. We hired a car service and driver, for 8 hours, to show us the Amalfi Coast from our hotel in Sorrento. This was sourced from the hotel's "land services" provider, and had a perfectly nice driver - but not an official, trained guide. Ten years ago, it was about 255 Euros. It would be much more today.
https://community.ricksteves.com/travel-forum/italy/getting-around-amalfi-coast
https://community.ricksteves.com/travel-forum/trip-reports/trip-report-2-weeks-of-day-trips-from-sorrento
https://community.ricksteves.com/travel-forum/italy/amalfi-coast-day-trip
