I am new to ethereum. I have a few questions.
Should I pre-buy gas to effect ethereum transactions? Or can I just set what is the gas price I am willing to pay so that at the time of transaction the gas will be purchased automatically and deducated from the original transaction amount?
When I am doing an ERC20 token transaction, should I still have enough GAS in my account or can I use ERC20 token to buy the gas live at the time of transaction? Can you help?