First cruise, what to pack?!

[wherewillwegoto]

We've booked a 7 day cruise in the Canaries for December but I've no idea what to pack! I usually wear jeans and sweater or jersey dresses in summer. I like v neck or deep scoop neck longer tops (at least 28 inches).

No shops except M&S where I live but happy to shop online. Also use Vinted a lot, so could maybe get better brands process preloved. Mostly wear blues/greens/grey/black, nothing pastel. Any suggestions? Thank you!!

I'd pack something similar to what I'd pack for a July seaside holiday in the UK.

I'm sure your existing holiday clothes are fine!
Which line? Some (British ones mainly) are much more formal than others (American ones).

The line is P&O.

The problem is I always wear casual clothing so no idea what to wear in the evening. We won't be going to the really formal restaurants, but would still like to dress up. I've a jersey wrap dress with short sleeves, but all my cardigans are scruffy. Maybe I need a wrap??

No one really dresses up unless it’s one of the posh lines.

P&O is relatively smart in the evening. You will want to plan for a formal night every 5 days or so which you'll need / want your best for. You can just wear it to dinner though and change into comfies to head to the theatre after!
If you really don't want to dress vaguely formally, you can skip the main dining room that night and use the buffet which is always casual, you would likely miss out on the 'best' menus if you did though. You can wear the same dress for multiple formal nights if you like, noone will notice.
There really are people wearing everything on ships so your dress will definitely be fine. I often wear very tidy jeans with a nice top & wedges. There are quite a lot of older people who cruise who typically prioritise comfort so you don't see loads of little dresses & heels.