Need suggestions on switching jobs.

Hi everyone, I'm looking to switch jobs for a better pay as my current CTC is 4.06 LPA which doesn't suffice me at all. Also, I have got many calls for interviews but out of them only 6 interviews got arranged and in those interviews as well I am unable to ace them at all. I'm trying to apply for a Java Full Stack developer. I need suggestions as to where I should concentrate and how I should prepare myself. In the last few interviews that I gave, the interviewers asked questions about creating small programs and they didn't ask anything about my current and previous projects that I worked on. I need some suggestions as to what I can do here in this case. Also, how much salary can I expect for a switch if I have to answer for an expected salary. Thanks.