Am currently in lake Garda :), it s sunny and beautiful here (though intermittently cloudy)
I would suggest
Pick 2-3 well fitting bikinis interchangeable tops/ bottoms give lots of options, there s a lot of lovely swimsuits around this year too.
Get at least 2 cover ups of your choosing.
I prefer block colours - have a cobalt blue, black and white options.
Personally I don't think the shirt option looks as good and chambray is a bit heavy and sticky in the heat (I know it s cotton but save it for when you get home to show off your tan).
Tie hair to loose bun at nape of neck - or French plait is easy too. I use spray on conditioner on hair when in sun (you can get some with SPF)
Neutral hands but coral/ red/ blue on feet (bring varnish to top up) (I prefer to do my own so they look fresh but get the shape and polish done before we go)
I m using mascara, bronzer (nars) and Bobbi brown shimmer brick (eyes and highlighter) for evenings and going out, and have coral lil gloss evenings (MAC)
Flip flops / sliders for pool side.
Sandals plus sundresses or skirt and top for evening, one of the loveliest looks I ve seen is loose wide legged trousers, off shoulder top, tan wedges,
I brought a navy white stripe skirt from oasis before we left - have worn it several times with coral/ red/ white/ tops and tan wedges for evening looks and I think it looks lovely !
Don't wear pool dresses or cover ups to restaurants.