If you have put all of the KP into a research and it will not unlock, then you are short some other item that it requires to unlock. As I am past that research, I cannot see what it requires, but is could be tools, coins, planks, marble, steel, etc. You should be able to look at it (hover or click) and see something listed in red.
I think the Magic Academy is a must have and would place it as soon as you can. That is also one of the buildings I suggest using diamonds to improve.
You're right, the best advice is to only build your boosted, clear provinces on your boosted good to get a better boost percentage, and trade, trade, trade. You should not have to wait long for your trades to be taken up by others. Don't wait to find trades that you can take, but place trades to keep your inventory even.