If you're not used to walking with poles and are fit and healthy, then don't bother to bring any. You can borrow one from the hotel, if you change your mind. I didn't think that any of the walks warranted the use of poles apart from for those participants with knee or hip problems.
I wore walking boots for each of our 6 days and that worked out fine!
The evening meals are enormous and you never know how many courses will be served so resist the temptation to fill up on bread with the first course!
No need to take anything 'dressy, as the whole holiday is very casual and relaxed.
Since so many parts of Pompeii are currently closed, we had about 3 hours there, then visited Herculaneum which was really good to help us to see how different the 2 Roman sites were. On our 'day off', we ascended Vesuvius and then some of us packed in Ravello too, just to make sure we'd seen everything on our lists!
If you're looking for a bit of early spring weather and greenery at the end of February, you may be disappointed! For our trip, the landscape was every bit as brown as the UK and we had snow flurries on our first day!