Well, let's complicate this.....
-1lb--this is the easy one: get 1 pound and it will last you a lifetime.
You don't mention any fish or other livestock, so I'm going to assume that this is a plant only tank.
First it depends on whether you want to get as little as you need or get well-stocked. I like to stay well stocked, but not everyone feels that way.
-1lb--I like to add a lot of extra K, but many people don't. Your call: for $3 I would get it just to have it on hand.
What kind of water do you have? Soft? Hard?
Barrs GH Booster
-1lb--If you have very soft water You may want to pick up a pound of this just in case you need it. There's a debate on whether added Ca/Mg is needed in even RODI water....I found that small amounts helped.
-1lb--If You have hard water it may have a Ca/Mg imbalance and adding extra Mg may help. That's my situation as well as many others. Can also be purchased as epsom salt.
CSMB and 10% Fe
are your call--if you are going to continue with the flourish (I do) then there is really no need to get either one.
If you want to get well stocked then double up on everything, execpt the KH2P04. Honestly, I don't think you need to double up. You don't have that much light over that tank, so 1 round of ferts should last you quite a while.