the title sounds like this is some sort of a club or something. "joining a lifestyle"
look up "zoonotic diseases" (i think there's a thread about them here somewhere) for more info on those. the general gist of it is most of these can be caught by any contact with an animal (not just sex) and like 99% are a non-issue if your animal is healthy and checked regularly.
stds are only an issue if you have sex with an animal after a human suffers from one. stds don't really jump species.
as for breed recommendation, it's impossible to give. we don't know your lifestyle or living conditions. the easiest for you might be to just visit any of the various breed picking sites on the internet, narrow a list down based on what kind of living conditions (care/exercise/space) you can give and work from there. and for the love of god, don't look up threads like "what breed has the biggest dick/bestest pussy" here, it's not something solely based on breed and shouldn't really be any of the reasons you're getting a dog.