I have lived in the tropics and middle east for a number of years and can offer some advice, it's not about price it's about fit and style, opt for long sleeves, you want to be able to roll them down to protect against sun and bites, loose fitting to let air circulate. I have never noticed much difference between linen and cotton other than linen looks horrible and creased, they wear differently also, linen seems to thin and Cotten holes...go for shirts with a collar
511 are good and tough, the shirts are vented and have loads of pockets, but the silicone coating is nasty, they don't wick sweat initially, you need to wash them loads before they feel ok, if you wipe your forehead on the sleeve it doesn't mop, they are ripstop and will probably last ages though, my white ones have taken a yellow hint from washing in less than clean water in the tropics and sand in the Middle East, nothing you can do to whiten them. Interesting I got them delivered to the UK and brought them back to indo only to find out they re made there and there is a 511 shop in jakarta....what a fool I felt....
For trousers I use cargos to like crag hoppers etc although they are synthetic, again always have long pants for bites and sun, always travel on aircraft and boats in long pants, avoid jeans in fact avoid any heavy cotton
When you watch backpackers they all wear Tshirts shorts and flip flops, they really are fine, not my thing though and you are susceptible to bites and sun asi have said plus you want to keep you wallet, cash and passport on you so swimmers are not a great idea in my opinion,
If you really want to stay cool use string vests under shirts, not sexy but they work, loose fitting underwear also unless hiking etc when I advise cycle type shorts
Someone mentioned Maglight, I still have mine from 1986, it's been used to bang in pegs and all sorts of other tasks, it still works and is the nuts as far asi am concerned, I have a whole load of them in different sizes, they are bullet proof
Dano