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.

It will depend of your revenue from ads, that's all.

If you have no knowledge with faucets, I recommend to you to left small amounts in the faucet with a low prize until you be ok with the bots factor because you will need some protection against this.

0.05 is a bit high, actualy you can start with 100.000 satoshi only and see the results.