You are self-employed. If you are a sole proprietor or single member LLC and not some kind of corporation, you are required to report your income on schedule C from your own accurate business records, regardless of whether or not you receive 1099 statements from your customers or clients.
Note that there is no magic source for one overall 1099 listing your income. A 1099-MISC or 1099-NEC is only issued by another business, if they pay one of their independent contractors more than $600 in a calendar year. If you have sales to individuals, they will not issue a 1099, and in many cases, even a business that purchases a product is not required to issue a 1099, depending on who is selling the product. (Apple does not issue a 1099 to Staples if they buy more than $600 worth of pencils in a year.) You are required to report your own income from your accurate business records.
You can deduct ordinary and necessary expenses. " An ordinary expense is one that is common and accepted in your industry. A necessary expense is one that is helpful and appropriate for your trade or business. An expense does not have to be indispensable to be considered necessary."
However, expenses are costs you pay for. You can't deduct anything for the value of your own labor. That's what your profit is for. If you spend 100 hours developing a product, and make a $10,000 profit, that's a very nice reward for your effort. If you had hired a software developer to code your business for $50 an hour, then you would have $10,000 of sales against a $5000 expense, so you would make less profit and pay less tax. But you can't deduct anything you didn't pay for.
If you have a computer that is used for business, that can be a deductible cost. If it is used 100% for business, that's easy. If used less, let's say 60% for business, you could deduct 60% of the cost, but only if you have some kind of reasonable records showing how you determined the business use percentage, that you could show the IRS if audited. Any equipment with a useful life of more than 1 year is an asset, rather than an expense. The cost of an asset can sometimes be deducted in the first year you use it in the business, but sometimes the cost must be spread out over the expected life of the asset (5, 7, 10 or more years, depending on the asset type).
Business expenses are discussed in publication 535.
https://www.irs.gov/publications/p535
You may want to schedule a consultation with a CPA who can tell you what you need to know about running a small business, including record keeping and tax obligations, so you don't get into trouble.
