I don't know if money is of a concern (getting everything at once gets pricey) but I would prioritize the things you need to get. First get the things that make you safe (lights, locks, helmet, vest), then the things that make you comfortable (racks, bags, fenders, jacket) and lastly the things that make you happy (computer, clipless petal, etc.). As long as you start with the things that make you safe, the rest is really just a matter of preference.