Firstly, if you have very less time, then you go for only 1 group.
Secondly, even if you have shortage of time, still go through the study material at least once. You can just read it as you read a novel or a story book. Reading once would help you to familiarize yourself with all concepts.
Then you may proceed with Suchita scanner and emphasize on quetions which are more frequently asked to increase probability of getting more marks incrementally with marginal efforts.
In case if you plan for Group 2 of executive, then you can take help of book " ONLY THIS MUCH". This book consists 600 pages approximately and it covers entire syllabus of all 3 papers of group 2.
All the best.