How can I get admission in bds having low ranking in neet

So unless you get the minimum cutoff which is given for a particular year which you will get to know after the results are published then you cannot be held eligible for counselling in any college from your Neet category of marks and rank
Yes at subsequently lower marks and rank you can apply to BDS colleges if you get a government medical colleges well enough otherwise private medical colleges
That too if you are trying to avail or out via the management quota seats in which is available in some private BDS colleges then you just need to have appeared for the Neet examination but that is a separate issue all together

Please specify what you mean by "low ranking". If you clear the cutoff you can apply to private and deemed colleges for BDS. The fee is higher in deemed colleges but you can get a seat even with lesser marks.