You won’t get banned for posting something rubbish (as you call it), unless it becomes a habit, and those posts get reported as being unsubstantial or of low value. That does require a fair share of recurrence for it to happen (the banning I mean), and it should not be down to a few bad posts here and there once in a while.
Having said that, it’s better to take some time to think your post through, and there is no need to rush to creating topics (as opposed to simply joining in on an already existing one).

Everyone is entitled to chase bounties here, although that does have its cost of opportunity in terms of ranking (and probably in diversifying some traces of knowledge gathered from different boards). One is also entitled to decide to pursue a change in habits, and shift their focus elsewhere.