I wonder if there are any 'best practise' rules when a man would like to start a family and grow up children according to the Jewish tradition and the Torah, if such a person should rather convert or remain gentile? I suppose there may be no rules or 'tips' about this, though. Is it also neccessary or recommended for a wife of such a man to convert (then the children are Jewish, in other case they would need to convert to be Jewish). I would like to remain in close contact with the Jewish community, but is that enought to consider conversion?
I don't think I exactly understand the question, but from what I understand you and your potential wife are gentiles and would like to have children and raise them as Jews. I think this is a very dangerous route because you would be raising non-Jewish children as Jews and it could cause a lot of problems for them in the future. Firstly, they would be utterly confused to be raised "as Jews" (which I assume means attending Jewish schools and keeping the Torah), even though they are not really bound by Jewish law. One of your options is that either you or spouse convert to Judaism, however, this option too is quite difficult because a Jew or Jewess is not allowed to engage in sexual relations with a non-Jew, thus it would create a major strain on your marriage and hamper your abilities to have children anyways. In my opinion, the only options are for both you and your wife to convert and then you can raise your future children as full-fledged Jews or that neither you nor your wife convert and you raise your non-Jewish children as such, but you can work on instilling into their education an appreciation for Judaism and Torah law giving them the option to convert on their own when they reach maturity. With the second option, I suggest looking to the "Noahide" community for support and guidelines (you can find more information about them online).
I hope I answered your question.