My quant is quite weak, I was thinking out leaving some topics like indices, surd and all- any suggestions on what are the hardest and time consuming topics I can leave out?

Read basics of everything to the level you can directly apply formula. You might miss the easy questions from the topics you're leaving completely.

If you want to leave topics, you can leave surds-indices, probability, P&C. Focus more on Arithmetic and Geometry and do at least basics of all other topics.