I have a stack of travel pots I use to decant my must haves into which for me are my lovely shampoo and conditioner (especially if going away cos I want to know my hair will look good), and I've whittled my make up down to several essentials that work really well for me - mini Laura Mercier eye stick, single shadow, Glossier boybrow,, eye pencil, blush, lipstick etc which for fortunately don't take up much room. Pressed compact. Brushes in bag. I decant foundation into travel pot and I take a superdrug serum/moisturiser (dead cheap) which I'm happy to share with the girls, use excess as body moisturiser or leave behind. Flying Tiger do good reusable travel pots. I take a Travalo atomiser for perfume. If feeling swish, I pick up a lovely posh lippy in duty free these days too.
Stuff I don't bother taking - either buy on the departure side in travel sizes or, my preference and if time allows because I love nosing about in European/overseas pharmacies, in a local chemists/supermarket - soap, toothpaste, deodorant, hairspray, body moisturiser.
If flying with Easyjet I now make use of their 'free of with Three' hands-free option if going for longer than a weekend, to drop off my hand luggage to go into the hold (then it's about six quid for return flight)...am in Spain now and it was great cos I had to bring suncream, Aftersun and mozzie stuff I know I don't get allergic reaction to and as there isn't a liquids limit on "hands free" and you get to take a tote bag (which they give you that effectively you can take a fair few extra things in...the bag is pretty ugly so I had a much nicer one to drop it into
) on the flight so got my lovely make up with me and bag had several bigger bottles in the hold that I'll either use up or leave in the Air BnB for next guests to make use of. For £6, worth it for me!