You can do a lot with 3 bitcoins but I would honestly do nothing like other people already said, I would just hold it for a while to make some good profit with it.
I'm sure that the bitcoin is gonna rise to a higher amount.
you cant do too much though, you can buy some stuff or invest it into trading only i think
Investing in trading is the best thing to do and you can grow them over a period of time and increase the number of coins in your wallets but that is only possible how to trade smartly.