You should start with the Greeks. Yes, this is important advice.
Chronology is important in philosophy, every new idea was a
response, restatement or advancement on what came before it.
Very few, if any major philosopher, is readable without an
understanding of what came before. If you take shortcuts and
skip a few thousand years then you will get lost and not get as
much out of it as you otherwise would. Three months is enough
time to give you a very basic overview and understanding of the
Greeks. It'll get you up and running. Also remember to "read
around" each author / work and study the cultural and political
events, happenings and attitudes of the time (and from previous
eras). Also understanding the art of the time helps too. These
heavily influence what a philosopher had to write. It's useful
to start off with short summaries of each philosopher to refresh
and expand on the knowledge you already have. Penguin has a few
useful books of this description and there are plenty of others.
Once you've read so