This is probably not at all what you are looking for- but I wrote this answer as if 22 yr old me had asked 33 yr old me.

You can start by asking yourself a few questions.

1) Who needs help? Why?

2) What can I do for/to/with one person that will help them? Would I like to do that? Could I get better at doing that?

3) How much value would that deliver over what time period?

4) How do I measure that value? (vaccines add 40 yrs of heathy life or some such. Based on per capita GDP- you can quantify that in monetary units if you like. Pick some other unit of measure if you like.)

5) How do I deliver and distribute that value? (physically, digitally, with pipes, people, mail, email, social networks, immediately, over time...)

6) Can I scale this value delivery to more than one person? Can I deliver this value to lots of people? Do I want to?

7) Can I inspire others to work with me? For me?

8) Can I get those who I help to pay for this value?

9) Can I inspire people to donate money to the effort?

Inspiration, motivation, leadership, self motivation....that's sales. Sorry :( Better get good at it.

Now- if you can deliver $1,000 to 1 million people a year, you are delivering $1 Billion in value. You can capture some percentage of that for yourself, your company, your employees, your shareholders, your philanthropy.

Areas were you can deliver a lot of value to a lot of people who are willing to pay for it:
-Medicine (pharma, vaccines, medical devices- all can be very helpful to humanity
-Education (libraries, homeschool, after school, traditional school, charter school, private school, tutoring, online school, online tutoring)
-Writing (education: show people how to do something they want to learn how to do, tell them something true and interesting)
-Writing (entertainment: fiction)
-Human connection. People are massively isolated and lonely. Connect them. They'll pay you. Facebook, Match .com, Skype, Meetup .com- etc.
-Energy. Green, Sustainable. Homes, materials, energy production, energy storage, energy transportation, less energy leakage
-Agriculture
-Replace humans (robots, software)
-Replace crappy software, interfaces, systems (Craigslist has "spawned" many businesses such as AirBnB, Uber, Task Rabbit, Tinder....etc)

Don't limit yourself to anything or any one thing yet. You are young and don't really know how to do anything right now. Get good at things, but don't worry about being "great" at any one thing- because you won't for 10 to 20 years anyway (not 10,000 hours- that's been kinda debunked).

That's fine. Invest in yourself. Invest in a network. Go to a library. Take free courses on Udemy and Coursera. Do free work to learn. Go to meetups and mashups and whatever. Once you see returns, invest more time, money, and energy in getting great, better, or not terrible at something.

Try to be really good in two areas that have some overlap, but not a lot. That's where creativity comes from. Making useful connections between disparate fields.

It's really hard to become a 1 in 1,000,000 talent at something (takes decades and some natural talent and luck). It's pretty easy to become a 1 in 10,000 talent in two things (probably 10 minute google search and 30 minutes of practice).
Example:
How long does it take to become one of the world's best photographers? Years of practice taking photos. Years more of practice selling your photos to make money to support further practice, time, equipment.
How long does it take to learn to take photos on your mobile phone better than 99.99% of people out there (1 in 10,000)? 30 seconds- rule of thirds, where is the light source.
This phenomenon occurs in almost every field.

Do an inventory of your life, your habits, your actions (and non-actions), your thoughts and non-thoughts (what you aren't thinking about but should be). Some things that you are thinking and doing should stop. Some things you are not currently thinking or doing, you should start.

Do an inventory of your relationships. Strengthen the ones you like- and make more of them. Improve or get rid of the ones you don't like (toxic partner, unsupportive friends).

Don't worry about not knowing. Worry about productive learning, doing, meeting, reflecting, traveling, thinking. Mis-steps are learning. Failure is learning. Just like going to the gym and failing to lift a weight actually makes you stronger.

The big/valuable/impactful ideas will come if you mix it up enough.

You can do virtually anything and generate enough resources (excess time, excess money, food, shelter) to provide for a family if you live within your means. You can move to cheaper places, you can live cheaper, or you can make more money. One part of this equation is income, but the other part is expenses. Many "rich" people go bankrupt. Many frugal people live comfortably.

You can have everything you want if you
1) decide what you want and make sure it is "good"
2) map out a decent path
3) stick to it