First of all, congratulations on having such a long-term perspective at such a young age! In terms of your question:
Q: What do you guys think is a good next internship?
The following should work well. Some options may not be possible due to your country and exact background:
- Consulting (ideally strategy)
- Startup (work for one)
- Startup (make yours grow)
- Strategy role in big brand
- Investment banking
What works best also depends on your country. You can easily reverse-engineer the best options by looking at where current consultants in your target companies worked in the past.
Additionally, given you already have work experience, you may want to focus as well on the brand of the university you are going to choose. It is a lot easier to break into consulting from a target university.
Finally, I would also take into account what you like for the choice of an internship – I don’t think it makes much sense to get a job that you don’t like just because it makes it easier to move to consulting later on.