In your re-application, you must
- be honest and transparent with your prior rejection
- actively take steps to address why your prior rejection, offering additional evidence on why your application this time shows further strength
- prove that this re-application is for a new trip (with different purpose); rather than applying with the same purpose as your prior rejected case
- avoid 'visa shopping' by applying to a consulate simply because it is easier than others. you must have your primary trip purpose identified first and apply via that country. If you visa shop, and they catch you, then you will get rejected;
I speak from my own re-application experience. See here for my story. I was eventually granted a new visa in my re-application for a second trip. I re-applied for a second trip with a different purpose and was eventually approved. It was not without considerable effort! I wrote a full cover to explain my prior denial in full transparency, attached details and excessive proofs for my next trip (hotel reservation, tickets to events, friends who I travel with and their info, etc.).
From my experience, you MUST be forthcoming with your prior rejection and you should know why your prior case was denied (if you don't, you must find out). It will be appreciate by the consulate if you proactively tell them and apologize and explain during your interview. If you try to hide, it will be really really bad.
For your case, since you got your first rejection back in oct 2018 I am assuming you are applying for a different trip with different purpose. So make sure you identify why you were rejected last time and deliberately explain the why and how you plan to improve this time. Re Greece, are you planning to go to Greece? Do you have sufficient proof that you are visiting Greece as a primary trip purpose? DO NOT APPLY via Greece just because it is easy! This is visa shopping!
I would agree that the reason "Justification for the purpose and conditions of intended stay was not provided The information submitted regarding the justification for the purpose and conditions of intended stay was not reliable" is probably the WORST out of all denial reasons; it shows that they just don't trust you. So you must gain back their trust by providing considerable more proof and evidence than a regular applicant.