Coal, let me ask this: are you running aftermarket headlights that have separate high and low beam housings? If not, I would not recommend running both high and low beam at the same time. You are going to generate too much heat in a very limited area if you are running halogen bulbs (especially if you are running the higher wattage bulbs).
As for the relays, if you are running halogen bulbs, then a 20 amp relay is enough for the low beams and a second 20 amp relay for the high beams. If you are running 35W HIDs for either the low or high beams, then you need a 30 amp relay to power both of the bulbs. If you chose to run the 50W HIDs for your high beams (if running in the low beams, talk to me first), then you need atleast a 20 amp relay for each bulb.
As for making the low beams come on with the high beams, as long as you meet my warning above, you can get away for much cheaper. Get your hands on a 1 amp diode that has atleast a 15V reverse voltage rating to it. Now, wire the diode so the black band on the diode is towards the low beam relay. The wiring will run from Post 87 of the high beam, to the end of the diode without the black band, then a second wire from the end of the diode with the black band to either post 85 or 86 (which ever has the positive voltage applied to it). This will force the low beams on whenever you have the high beams on.
As for the fog lights, they already have a relay powering them. So, no need for a relay harness for them.
