Pearl Islands
All-Stars
Micronesia
Gabon
Tocantins
Samoa
Heroes V Villains
Nicaragua
Redemption Island
South Pacific
One World
Philippines
Caramoan
Blood V Water
Cagayan
SJDS
Worlds Apart
Cambodia
Amazon, Palau, Panama, Cook Islands, China & Kaoh Rong (the current season) are all must watch IMO. Borneo & Australia are really good old school seasons but if you don't like slow gameplay then i wouldn't recommend it.
Marquesas - if you're a Boston Rob fan; otherwise don't bother.
Africa, Thailand, Vanuatu, Guateamala and Fiji are not really worth watching if you are a casual fan.
But at the top of my list - The Amazon, China & Palau are really awesome
Sorry for the extremely long post i'm just trying to give the best advice here lol