There are two ways to pay taxes for domains. Inventory or investments.
If you are constantly buying/selling, the domains are an inventory. Just like store items. If you buy a domain then you don't deduct it off your expenses. You pay taxes on inventory only once you sell it. So if you were to buy domain A, you wouldn't be filing it with your taxes until you sold it. Therefore you only pay tax on the profit of that sale.
If you are investing into traffic domains you can deduct them off your taxes the day you buy it. Then you just report all the revenue that comes in as profit.
I think that's as simple as it can get.
I'd recommend a good book over an advisor. Atleast you'll be educated yourself. Don't always rely on others!