Welcome to the forums! I think the best way to start is to look at some of the pictures available here and decide which version of Fett you would like to be. There are differences in the versions, some subtle some not so.
Once you have made that choice then you should look at your budget to determine how you will build it and which parts you might want to start with. I think the armor is the easiest place to start and it can cost as little as $30 to do or over $300, depending on your approach.
You may also want to start looking for a helmet - these can take a LONG time to paint correctly. Ultimately the choice on a helmet will come down to budget, time, and (from my standpoint anyway) your size - a mystery helmet won't look so good on your if you are only 4'9"
There are some folks here that make some awesome raw helmet bases if you decide to paint it yourself. There are also some true artists here, not always the same people as the bucket makers, who will paint it for you if you have the budget and don't feel comfortable doing it yourself (though for me that's where the fun is).
Anyway, that's the way I would start if I were doing it again. Look around, see what others have done, you'll quickly find out who makes what and find the threads where people give you the "how to". Check the "sticky" lists in the various sections as well. Try not to feel overwhelmed and most of all, have fun!