Montserrat is a really great country to start with if you wish to collect the reign. The stamps follow the usual pattern of most other colonies, and are straight forward and simple. Like most colonies, there were two definitive series.
The first was the monochrome set issued 2 August 1938. The first printing (the 1938 printing) was perforated 13 x 13 1/4. It is rather difficult to find used. There were not any colour nor shade varieties.
The second printing of the series (1942-1945) was line perforated 14.
The different printings between 1942-1945) yielded some colour varieties and a few flaws.
Here is the second printing to the 1/-...

The second definitive series, was issued 17 September 1951. Here's the 3-cent stamp from the series...

Montserrat is a small colony, so you could probably have an interesting postmark collection from there, as well.
Enjoy!
David