I will suggest don't open faucet as these days running faucet is not profitable if you can't get thousands of unique visitors everyday and also obviously not the bot traffics. Main problem is with low paying bitcoin based adnetworks and google adsense suspending all bitcoin faucets.

But if you want to open faucet i think 0.05 bitcoin could be enough to run faucet for 10 days around in starting days if you use faucetbox free faucet script.