I collect British Colony stamps. Primarily the stamps issued during the reign of King George VI (1937-1952).
The designs are very attractive and most of the stamps were engraved, so they are pretty attractive. Due to changing conditions during World War II, there are a number of interesting variations in the paper, gum, perforations, and the ink that was used to produce these stamps.
As a result you can create a basic collection or become very specialized. It is an interesting area.
Years ago I started collecting KGV stamps from the British Empire, mostly because everyone else around the bourses were collecting KGVI. The internet has been a blessing to fill those stubborn gaps - there were some stamps that never seemed to turn up here in Australia in the 1990s.