I think manual approval for every newbie will be too much work for moderators. But I support Jet Cash's proposal:
Curious to know which boards should be open for them
It's not "closing new registrations", it's a practice which is common in many popular web forums. Beginners & Help (and similar sections in the Local boards) would be the most natural "cage" for newbies - in other sub-forums they should only be able to post on threads created by others.
Maybe one could also create a minimum length - for example, 100 words - for newbie posts (at least in the on-topic boards). While they could try to circumvent this restriction with copy & paste, that would be clearly a violation of the forum rules and so these people can then be instantly banned.
Just block posting by them on most of the boards.
In other word you are saying to close new registrations Curious to know which boards should be open for them
Maybe one could also create a minimum length - for example, 100 words - for newbie posts (at least in the on-topic boards). While they could try to circumvent this restriction with copy & paste, that would be clearly a violation of the forum rules and so these people can then be instantly banned.