Is 40 or 20 GWEI too low for gas price?

I am trying to do a transaction and only have $19 worth of ETH in my account and I need to send 3 transactions so $6 max I can afford. Ledger saying 62905 gas is required and if I choose 40 GWEI, $5.995 is required, 20 gives me $3. Can I also go lower? How long do I have to wait for 40, 20 or lower? A day or just few hours?