If you are operating as a sole proprietor (reporting on Schedule C), the potential expenses deductible from your gross income are too numerous to list. The publication at the link below is a good place to start.
https://www.irs.gov/publications/p535#en_US_2018_publink100015064
The IRS also has a web site for self-employed individuals.
https://www.irs.gov/businesses/small-businesses-self-employed/self-employed-individuals-tax-center
