How much should I ask for my foils?

Hello, All!
I am a new Magic player - joined between Legions and Scourge.  I've
participated in a few drafts and bought some magic grabs and boosters.
My card pool is very shallow - about 700-800 cards not counting basic
lands (which, to my surprise, seem to slowly accumulate).  I already
have a few foils - from 8th Edition and Mirrodin.

I'm not so fond on foils, but I know some people are.  Thus, I plan to
exchange my foils for some cards so that I can build a decent deck or
two (preferably even more).  Here is the list of my foils:

Coastal Tower x 2 (8th Edition)
Evacuation (8th)
Star Compass (8th)
Dusk Imp (8th)
Standing Troops (8th)
Dross Scorpion (Mirrodin)
Cobalt Golem (Mirrodin)
Plains (Mirrodin)
Nightmare Lash (Mirrodin)  (I'm not too excited about giving that one
away as for now it's my only one)
Wall of Blood (Mirrodin)
Thorn Elemental (from 7th Edition Starter Box)

So, will the above cards buy me a box of Mirrodin or 8th?  Or should I
ask for more?  I can throw in some regular cards - I have, say, Serra
Angel (and since I also have two Blinding Angels, I most likely will not
need the good old one), Savannah Lions, Coastal Piracy and some more,
but I'd rather stick to them and experiment with them.

Another question: some guy around here is looking for black-bordered
Dark Rituals and I have two.  How valuable they are?  May I, say, ask
for Akroma or Decree of Justice?  Or are they worth more?

Thanks in advance,
    Arkady.