First, you don't absolutely need an HDMI cable. There is only an imperceptible visual difference between HDMI cables and component video cables. The main difference is that with HDMI, you've got one cable for both audio and video, while otherwise you'd have perhaps five cables (red, green, blue, left, and right).
Second, how many cables you need (and of what types) will depend a lot on the specific components you have, and whether or not you have an A/V switcher. (I recently purchased my first, and it surely makes having a cable box/DVR and a Blu-ray Disc player a lot more convenient.) If you indicate the model numbers for the devices you're getting (for FiOS, just indicate what type of equipment you have requested, or already have), I can probably find the specs and give you some better insights.
Third, don't pay more than $4 per HDMI cable. You can find the correct cables you need, for that price, at monoprice.com.