Dear aspirant,

In Delhi some of the best coaching centre for RBI grade B are

TIME

Career launcher

Vidya guru

Career avenues

Mahindra institute

Success mantra

Pioneer academy

Institute of banking training.

However you can also go for online classes for your preparation. As today everything is going online so you should 1st check you tube and go through channels and teachers . While selecting a channel just see how teacher is teaching , are you able to understand, are they teaching relevant . The relevancy could be checked by comparing their content with previous year paper content. Also you need to check that are they mostly involved in marketing ,if they are then the channel is not so good because for those who are really good and provide.good guidance and preparation to students does not rely on marketing , the only marketing  they do is Word of Mouth.

So you may check both the options and select according  to your needs.