What was the first transaction which resulted in the very first bitcoin being mined
It startet with the rewards of the first blocks. After the genesis-block, there were 50 bitcoins in total, after the second block, there were 100 bitcoins in total, 150 after the thrid block...

This is the first block and the only transaction is a coinbase transaction (reward to an address). https://blockchain.info/block/00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048

And the following blocks do all look like that (only the coinbase transaction in all those blocks) until Satoshi made the first transaction from one address to another address (in block #170)