I recently became a GC holder. How does the Obamacare and Financial Aid works?
Very confused. Please enlighten me...

If your employer doesn't have health care insurance then you can go to
healthcare.gov and get quote and see how much insurance you can get.
For eg one of the folk i recently helped had 26K annual income
he got quote of $195 for silver insurance for Carefirst and Obamacare better known as ACA
paid him $110 and he has to pay $85 per month which was not possible before when his company decided to not give health insurance and pay fine.
All cases vary may be your employer gives cheaper health insurance than healthcare.gov
then you can take that which is true in my case.Please play around with site and read you will get your answer.Hope that helps.

Also if you don't want to work you can apply for food stamps in your county or I would suggest you better go to college and get government financial aid like Hope credit and FAFSA and get some degree and be at level where you don't need financial help that is the route I will take if I were you based on what level you are.
Also you will have better access to small business loans and cheaper mortgage based on your credit history and what you want to do.
There are lot of US citizens and GC before you so don't think having that will solve all problems.