I can't advise you about army as I am not from your country.
But I will share some advice based on my past experience and knowledge.
Usually I will plan my future/career based on the following:
1)Interest, strength, aptitude:
Usually I will choose to study/pursue a course/career based on what I like the best and what I am good at.
During my school days, I like Maths and that's how I ended up in Electronics Engineering.
So, pursue something that you like the best and good in it.
Also, try to have a few options in case you don't get your favorite course/ career.
Having double degrees will give you more options when choosing your career in the future.
There are also people who switch their career in their mid-life (30-40s).
For example, you can start your career in military but ended up as a businessman or doing something else in your mid-life.
2)Job market, job prospect and job security.
The second most important point is, ensure that the course/career enable you to find job easily and this will ensure better job security.
In my country, most people will try to get government jobs because they pay well and you rarely have retrenchment in the government sector. The retrenchment is almost zero in the government sector though the promotions will be slow.(one negative aspect for those who are more ambitious).
The jobs market keep changing. Nowadays, software engineers and firmware engineers are quite in demand.
Jobs that deal with internets or Internet of Thing (IOT) such as cyber security analysts are in demand nowadays.
Jobs that deal with our basic needs will always be in demand such as the doctors, pharmacists, nurses (healthcare industry), food & beverages industry, etc.
3)Salary
Lastly, ensure that the job pay well or have a decent pay.
In my country, one of the jobs that pay very well are doctors or senior consultants especially cardiologists. Each heart surgery cost ten of thousand dollars.
We also have cosmetic surgery doctor who become millionaire within a few years of starting his own business.
When you have a lot of money, you can always pursue your hobby of fish keeping.
You can even have a big marine tank in your house and buy all the expensive fish and corals/reef.
Some beautiful and rare marine fish can cost a few thousand dollars. You can buy all the expensive equipment for your marine tank.
You can even hire people to maintain your marine tank.
Some extra:
Education is usually the quickest way to have a good career and future.
But some people used their skills/talents(photographer, artist, musician, actor, hair stylist, car mechani, etc) and knowledge or business sense(businessman) to make money or earn a living.
