Noob to the Gwei, have a question.

So im trying to do a transaction with ether and i never have before so i read up on the whole gas situation. Very high but fluctuates. Im using metamask and i see i can kinda put in my own gas prices to happen slower but eventually get picked up. how low can you go before it is never picked up at the time? online a lot of info is outdated for the current wei climate from what im seeing.