Here are some things to keep in mind, come tax season, if you stream full time. 

Since your donation, sub, and ad revenue are considered self employment income, you are able to deduct against that income applicable expenses.

IT IS IMPERATIVE THAT YOU HAVE DOCUMENTATION FOR ALL DEDUCTIONS IN THE EVENT YOU GET AUDITED.
-Receipts
-paypal statements
-credit card/bank statements

Any games(virtual or hard copy)or accessories that you buy for streaming are considered supplies.

Most systems/computers will need to be set up as assets and depreciated over the life of the system. This means you can only 
deduct a part of that expense in the current year. Then you can deduct the rest over the "life" of the asset.  It varies from computer 
to consoles and even from computer to computer.  You'd have to check to see what the "life" of the item is then divide the number of 
years into the cost and deduct the result annually. If the system is really cheap, you can get away with classifying it as supplies.

The following are intangible items you can deduct:
-Antivirus Software
-bookkeeping software (if you use it to track your stream's financial info)
-donations/sub fees to other streamers (classify this as "stream expense" under other expenses)
-monthly internet fees (you can't stream without internet)

It's a bit of a stretch, but if you buy clothing that's primarily for streaming, that's deductible under uniforming. For example I intentionally get Pokemon and other nerdy t-shirts to wear on stream.

Marathons that you attend like AGDQ are considered "business trips".
-Your fee for the badge is deductible.
-Meals that you pay for are partially deductible (keep track of all of them, and a % is able to be written off.)
-Plane tickets/cab fees(including uber/lift)/rental cars, tolls, even paying a friend gas money (It's best if you use your card and get 
 a receipt) are all considered travel expenses.
-If you drive there, keep track of your mileage (even if you didn't drive that far).

If you have a PO box that you use for any stream related activity, such as gifts from viewers or to receive stream equipment you've ordered, you can deduct the fees you pay for that PO box.

If you hire an accountant to do your taxes that's deductible under Professional Fees. For example, the fee you pay for 2016's taxes is deductible in 2017, because you paid for it in 2017.

You can deduct some of your other at home expenses. 
-Rent/mortgage interest
-power and other utilities that you need to stream

You need to have the square footage of your home and your "office" or stream room.
You divide the square footage of the office by the square footage of the house/apartment and that percentage of the above bills is deductible.

Even if you make a small amount of donation revenue from streaming you still want to (and are supposed to) claim it when you file.  Rent and power alone will likely be enough to more than offset that income giving you a "loss" which will lower your taxable income. 

Not all of this loss will be deductible in the current year, but it will carry forward to future years until it's fully deductible. All directly related expenses will be deducted in the current year, but the portion of indirect expenses (rent and power), are only partially deductible.  

You still want to account for everything, because the carry forward can help lower your tax liability in future years.

If you didn't have to pay for it, then don't worry about including it for tax purposes.

If you are a big time streamer, you may want to look into making estimated tax payments to the US Treasury and your State's Department of Revenue (for states that have income tax). You can do this monthly and quarterly.  In some cases you can incur a penalty for not making estimated payments if your tax liability is high enough. You can find more info and payment vouchers here: https://www.irs.gov/pub/irs-pdf/f1040es.pdf  You'll need to look on your state's website for their requirements, as those vary from state to state.

If you're a super big shot, and need business cards, those are deductible too.

I will add more to this as I learn more info.