Clothing: Almost all suggestions are to go with cheaper, washable suits and spend money on good, quality shoes as missionaries walk a lot in this mission (Cole Haans and waterproof boots like Bogs have been mentioned). Some missionaries will go through 4 pairs of shoes. Quality socks are also helpful.
The Alimen's and Gentle shirts have held up great and still look nice even after a year into the misison. Get pants that are quick-drying material.
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Most parents send their Elders with at least 1 suit (most countries in South America only wear suits to church and meetings) and around 8–10 golf pants. Families are sending more shirts because of heat and humidity — 12–14 is the average. Note for Sisters serving in Brazil: feminine hygiene products are expensive there and tampons are often considered taboo. Be prepared to send a good supply with your Sister Missionary.
Serve shirts have a ventilation panel in the side of the shirt making them noticeably more breathable. Missionaries serving in hot or humid places absolutely RAVE about this feature. The most popular shirt for hot-climate missions, for sure.