I've done loads of cruises and my favourite was NCL escape last summer around the MED for 10 days.
Do not go on Marella. (My opinion having done 10 plus cruises)
NCL has free at sea which is basically really cheap drinks package which is popular, but bars were only busy in the sea day. We did the upgrade where you bid on an upgrade and got a spa balcony which was absolutely brilliant and we had unlimited access to thermal suite which is so beautiful. Drinks package included soft drinks so worth it for that alone as it's so cheap and you get wifi etc. I think it's £149 for 10 nights for 5 benefits (drinks, wifi, 2x dining, shore excursion credit and something else)We flew to rome.
I'd also do a a P & O from Southampton. More attractive as there no cheap drink packages and no flights but colder sea says in the way there and back. I've done a P AND O fly cruise. Advantage is it's in sterling.
In fact my first cruise was a PO CRUISE AROUND ITALY and it was fabulous. Can be a quite dressy on elegant night. Food was great.
Loved princess cruises for the food and service. Royal Caribbean is ok too. MSC is ok but I'd avoid for a first cruise.
I'd try celebrity as they are also a premium luxury line but not done it yet.
NCL and RCI are classes a premium resort ships. No posh nights. Fun atmosphere. Still luxury.
Get a balcony. Ensure tips are included and included on a drinks package. Have fun. I'm going to Alaska this year 🚢 🐋
Most days we get off and walk about have drink and snack and get beach on board!
Go for a newer ship. Escape isn't the newest but it was beautiful.
There are tonnes of cruise you tubers. Sometime the don't give a balanced view as they do it as a job they get paid for so don't want to slate the cruises (even if they do pay for the cruise, the content pays their living).