In 2015, I worked full-time from home as an online English teacher. I was paid by a foreign company, but I invested money into my future business (e.g. computers, microphones, websites subscriptions). In 2016, I will be offering services on my website as well. Because I was paid by a foreign company, I do not have the 1099-MISC form. I had no income from any other source. How do you suggest I file?
You are self-employed, even if you didn't receive any 1099-misc forms. You would enter your income received and associated expenses in the business income section of TurboTax Home & Business.
It seems most people adopt the determination of independent contractor status at face value from the company paying them. There is more to the story.
https://justworks.com/blog/consequences-misclassifying-workers-independent-contractors
I would encourage reaching out to the IRS for a determination specific to your situation.
https://www.irs.gov/businesses/small-businesses-self-employed/independent-contractor-defined
If you believe that you have been misclassified, you can ask the IRS for a determination.
https://www.irs.gov/pub/irs-pdf/fss8.pdf
This can result in substantial savings realized in the difference between the self-employment FICA tax and the employee share if it is determined that you are an employee. It also poses substantial financial risk to the erstwhile employer.