Here you go:

In my experience, practicing 15-20 cases is sufficient, if you do it strategically. My recommendation is as follows:

• Read up on the typical approaches and standard frameworks to get the concept.
• Then, do 5-6 cases to get a practical feeling for what a case is like. Start with easier ones - e.g. market size mini cases, simple profit tree cases, etc. This will help you develop a rudimentary sense for how cases work
• The next 5-6 cases should cover cases from all major types and help you gain the experience and comfort with standard frameworks and the thinking required for solving the cases.
• Lastly, you will want to do 6-7 cases to hone your skills. Practice with people who understand what they are doing - experienced interviewers, coaches, etc. that can give you 1-2 main items of feedback after each case that you can then practice to apply and improve on in the next case. During this time, you should also practice to move away from off-the-shelf frameworks and tailor, or - even better - develop your frameworks specifically during the case.

The further you move towards the final interview, the more important it is to practice with experienced interviewers. While you can easily ask any friend or practice with peers for the first few cases, you should aim for qualified, professional feedback as you approach the finishing line.

However, keep in mind, that this requires a strong plan and strategic approach to the preparation. I regularly see people doing 30-40 or even more cases. While this can also lead to success, in my eyes, it is a bit of a waste of time, especially for experienced hires that often also have a regular job to do while preparing for the consulting interviews.

Let me know if this helps. I'm also happy to elaborate any of the above in more detail. DM me if you like.

I have a similar background so it might help you.
So here is how I did my prep : there was two phases. Phase 1 to prepare for the case and phase 2 for the fit (both are really important).

Phase 1 : preparing for the case

• I read the case in point. I learned the principal framework and read the transcript of the case interview that are offered. It's useless to learn the whole thing by heart. Learn the framework in a smart manner which means learning the framework but most of all understanding why there is each part in each framework and not others. You will quickly realize by yourself that some parts in the framework aren't that important while other can be treated differently. But it gives you a nice basis.
• Practice cases on preplounge. The first case was terrible. It was seriously pathetic but that was a very good and necessary experience. I didn't really know in which direction to go or to apply the framework and so on. But i kept practicing. I did between two and three sessions per day (three is a little bit too much IMO : you're washed out for the third one and don't really gain much from it). Two sessions means four cases (two as interviewer and two as interviewee). This is very important to do both as you will see the other perspective which will help you to drive the case.
• I practiced until I got confortable with cases. When you start to see where the case is going, don't need to take too much time on delivering your structure and start to realize on your own that this is the end of the case. This time varies from person to person but you need to practice until you reach that point. I didn't prepare for specific type of case or industry. I did anything that was offered. There is no point IMO to do only specific industry or type of case (profitability, etc.) . Quite the opposite.
• When I reached that point I booked a case with an expert. Very important to gain confidence and see what was wrong and could be improved. My feedback was very positive (not much to improve)
• Then I knew i was ready to go. So i kept practicing cases but not as often. Only two times per week. Just to stay sharp. And every know and then I only read previous cases to refresh my memory on what i could have improved at the time and what was important.

it was only as of this moment that i started to do interviews.

The duration can vary from person to person but I would recommand to estimate the preparation to be at least 6 weeks. In total it took me around 30 cases before getting really confortable, seeing any case as a nice exercice instead of being stressed by it and being able to deal in a correct way with all the cases I was given. After those 30 cases and the session with an expert I maybe did between 5 and 10 of them (at most). And when i had interviews I always did on prep session per week (two days before the real interviews). Those final prep sessions were all simulation of real interviews (so FIT+case).

In the meantime, every now and then I read the economist, analysis from Mac Kinsey, BCG and Insead. It doesn't take long. Half an hour every couple of days or something. I personnally read it in the subways or while i was cooking. Just to see the problematic and gain some insight. I also did some market sizing on my own every now and then. It takes few minutes and you get confortable with that very fast. I also watched few videos on Youtube since there is a lot of material from former or current consultant (personnally i watched rocketblocks but you have plenty of choices).

In parallel, I also prepared the fit part.
I just did it every now and then on the side. Nothing too systematic but a constant effort. It was always in the back of my mind and then i really practiced it during 1-2 weeks.

It can seem like a lot but this is manageable. Really. The only difficult part is to understand how it works. This is the only bottleneck to crack. With your background you already know how to read data and plot and are probably already confortable with numbers. So you will not have to work on those parts that much compared to people with other background. People insists a lot on the "business sense" but you'll see that at some point it's nothing more than simple common sense.

Among my inner circle we were 7 people that tried to go into consulting over the last 2 years with scientific background. None of them had any experience in business. Only one didn't make it. Among the 6 that made it, 2 out of 4 made it to MBB. The other two (I was one of them) didn't shoot for MBB (because they didn't want to) and joined tier 2 and small boutiques (same for the two that failed MBB).
In total, I personnally did a little bit less than 10 interviews with three firms (some firms have two interviews per round). And i always made it to the next round. And I'm far from being a genius or anything. When I got the offer from the company i liked I stopped the process with the other two, so there is no guarantee I would have had three offers if I kept going.

I'm not saying that it's easy

Far from it. But it's definitely doable. It takes motivation, preparation and dedication. But you can do it even without any background in business or cases experience.

Good luck and don't worry. It's definitely worth it!

Congratulations for the offer!

I'd recommend to reaching out to them. Nothing bad will happen if you don't, buit it never hurts to keep the connection alive to establish a connection already before you arrive in the office. See it more as the first step into your career.