military brat/ex wife here we are experts at packing.
1 - plan to wear your heavier/warmer items while travelling, and layer up.
Generally a good idea anyway as departure lounges and planes tend to the cool side, this includes wearing trainers/shoes/boots too, also make use of pockets for small/portable essentials like charger cables, combs, pens etc even smaller items of make up in your case
2 - multiple use clothes are your friend
Fancy flip flops maybe with a slight wedge heel so they work as both flip flops and sandals, most cases even cabin size you can unzip the lining to put shoes and anything else that might catch in that part zipped away from the clothes
Thin scarves to use as scarves, wraps, bags, sarong etc very versatile and if you get a few in the same palette you can even layer them for a thicker "proper" skirt or dress look with no chance of a "wardrobe malfunction"
vest tops to use as tops, bra subs
(I'm quite busty and I haven't worn a bra for years), layer for cooler tasks/days
swimsuits/tankini's that also can work as the top of an outfit with a skirt and wrap or even cardigan added
Other than that thin, light and either crush resistant or look better a bit crinkled items like summer strappy dresses, loose trousers/shorts, gypsy tops, underwear can be the teeny string type but even if you want to take a couple granny pants pairs they take up little space, and can easily and cheaply be bought there. If you want to get creases out as soon as you get there, twist the garment, wet your hands in cold water and wet the garment with them, then untwist and "flap" the garment and dry off quickly by drying with a hairdryer from the INSIDE of the garment in short bursts - I know twisting sounds counterintuitive but it works
3 - multiple use items -
recommended to me on here is a travel usb multiway adapter I got from amazon. It can charge up to 4 items at a time and comes with different parts to adapt to foreign power supplies think it was this one:
www.amazon.co.uk/Lencent-Charger-Universal-Adaptor-Worldwide/dp/B07QMVB2WK/ref=sr_1_6?dchild=1&keywords=usb+travel+adapter+lencent&tag=mumsnetforu03-21&qid=1622067629&sr=8-6
I got one for myself a few years back and I love it and then dd was going on her first adult girls holiday and I got one for her (which she initially protested) and she was very popular on the holiday!
4 - make up - pare it down to basics
A stick style foundation (given our complexion I'd recommend one with an spf included), maybe powder (use a puff instead of a brush), small eyeshadow and one lipgloss. mascara can be skipped I think as it just runs in the heat anyway, the idea to get lashes coloured before holiday is a good one. Or else a tiny slick of vaseline (a small pot is very handy for various holiday uses, I recommend sticking to the original its more versatile if you need to use for 1st aid etc) that'll keep your liquids to a minimum too.
Neutral colours work best and you can add a small pot of a shimmery gel to glam things up of an evening
I'm also a freckly redhead with a birthmark on my face to boot! embrace your natural colouring, just make sure good sun block! I also go red in the slightest hint of warmth and never tan, even fake tan looks seriously weird on me! embrace the pale and interesting, trust me the portuguese will be wowed.
5 - hair - keep it simple
Plan on mostly having it either loose or tied up in plaited style or loose bun, practice before going if you want to feel more confident. I have long, wavy hair that can be murder to tame, my go to easy but looks like it took more effort option is a loose chignon, brush back into a low ponytail, twist it right to the end, tuck the end in, place firmly in centre of back of head and clip in place with a barette or crocodile clip, takes mins, looks like you've taken hours once you're well practiced and its smooth and tidy.
crocodile clips also work as clothes pegs for light items, heavier items you rarely need to secure
If you really want straight hair, you don't necessarily need straighteners for this, I was straightening my hair long before they were a thing just buy severely drying it! 
just using a hairbrush and dryer, brush to the end wind hair so it's held on the brush and dry that section, I'm sure these days there are umpteen youtube videos showing this technique
6 - toiletries
Unless you have severe allergies, just buy them there and dispose of at end of trip (try to buy small packages so not too much waste, and share things like shower gel, shampoo and even toothpaste and mouthwash, there's usually wee mugs for mouthwashing anyway), otherwise decant your favourites into small travel bottles, remember liquids rules for travelling.
first aid - the sunburn thing! I would highly recommend you rtake a small bottle of lavendar essential oil, one of calendula oil and if it can be managed a small tube of aloe vera gel in case you do burn.
They can be combined to make a very effective and soothing after sun gel, you can also put the oils in a tepid bath if you have a bath available (4 drops lavendar 3 calendula) or make a basin of tepid water in a sink, add 2 drops of each oil into the water, then pop a bedsheet or small towel in the water to place on your affected skin, could end up helping you get a decent sleep even if you do burn, its horrible getting burnt.
Hopefully you won't and you'll have a fantastic time.