how much dwarfs must have to find a block ?
If you want to do Hive mining then please first read this post, it will help you to understand how Hive mining works.
https://www.reddit.com/r/RingCoin/comments/fjmgph/hive_mining_basics_how_dwarves_work/I think 100 dwarves are okay to find a block. But, I heard that atm all members are not getting profit with Hive mining. So, if you want to do hive mining you need to start with small amount e.g. 1k - 5k dwarves. If you make profit then you can increase gradually. But, before going for hive mining make sure you have some incoming connection along with a good number of outgoing connections.
If you want to know more about hive mining then please come to Discord and drop your question in
ring-hive channel.
https://discord.gg/3AnFpvyNote:At the moment there are some other factors that are affecting Hive mining which were not expected. Devs are trying to fix those factors/issues.