After realising some years ago that no matter where I went or for how long, I wore at most a quarter of what I packed, I developed a strategy that works for me:
I have a 'holiday wardrobe' that rolls on from year to year and is rarely seen at home.
I ignore fashion - I always want to wear things on that are comfortable (natural fibres,) and flattering (not too much flesh).
I look for my holiday basics all the year round, and mostly find things in sales. The bulk of it has been going strong for years.
Often my beachwear is not intended to be beachwear - it might be a winter season oversized shirt, but it works with my look. Real clothes seem to travel well from from beach to bar to going out.
Most of the time, even if I'm staying somewhere really smart, I don't worry too much about the evenings. If it's hot I really don't want to be trussed up, so a simple dress is enough.
I travel in white converse, take metallic birkis for day, and some smarter metallic sandals for evening. This way all the shoes go with (almost) everything. A bigger bag can be hand luggage and beach bag, and a small strawish looking one goes with all but the most glamorous looks.
I take a maximum of 3 bikinis. As long as there is one dry, then that is enough.
A hat is good. I also use a spray on hair sunscreen. Korres do a great one that isn't too greasy. (I think they sell it in Waitrose now.) For the simple clothes to work, the hair needs to stay looking in good condition. Sunburn really ruins the look, too...
I do decant all the basic stuff like shampoo into small bottles (Tesco do quite good ones, or did last year), because I don't want to surprise my skin/hair with anything new. And I take minimal makeup. And anything that might leak is double wrapped. A footfile is good for keeping on top of the dry heels.
Hope some use!