First, I used an all natural make-up look. Here is me in the car. I'll give you a tutorial of natural make-up soon. Never forget the sunblock before your make-up if you are going to the country.
A big, very light shirt is the most comfortable option in order to not feel heavy and have freedom of movements if you are planning to walk a lot, and shorts (for me, are the most comfy).
Remember in the country it generally gets chilly in the afternoon, so it is a must to have a warm cotton cardigan with you.
And good walking shoes, preferebly old, so if you get in the mud, or they get very dirty you don't spoil them, and also closed, to avoid any kind of bug bite :)
Remember: Repelent is a must for the afternoon and night.
And also a cheap pair of cotton pants. Don't go for the expensive ones if you wanna do many outdoor activities, they are for real gonna end up messy.
They will help you from the cold and protect you from the bugs in the late afternoon.
It is good to have with you: Sunblock, mosquito and bug repellent, a towel (in case you fall in the water or you get splashed by the fishes), another pair of underwear (again, if you fall on the water), and an extra shirt and afer-sun gel or cream. If you are really sensitive to bug bites, they sell in all the drug-stores special creams to put on the bite after it, they calm the itchiness and rash.
Forget about being too fashionable, in the country you have to feel comfy and free of movement. Light, baggy and comfy clothes that you wont regret if it gets ruined.
If you don't like pony-tails, you might hold your hair in half pony-tail to avoid having hair on your face :)
If you are not too familiar with the quietness of the country an mp3 player is a good idea.
Large shirt: Got it on a sale for around 8 USD
Shorts: H&M for around 12 USD
Shoes: Got them in a sale for 6 USD!!!
Cardigan: you already know it ;)
Cotton pants: Got them in a cheap store for around 8 USD