How does the full lifecycle of a cryptocurrency trading look like? I am new into cryptocurrencies and I am wondering how to trade them. By trading cryptocurrencies I mean:


Transfer fiat currency (ie. USD) from my bank account into some account that enables buying cryptocurrency.
Buy a cryptocurrency like BTC or ETH with fiat currency.
Transfer cryptocurrency back to USD.
Transfer USD back into bank account.


Is there one platform where I could accomplish this full lifecycle of a trade?

From my research I was able to create a cryptocurrency wallet with Atomic wallet. This app allows to transfer USD via credit card into the app and then trade USD with multiple crypto currencies. The fee for transferring USD to a crypto is 12% of the amount. Which does not make much sense for serious trading (I need to pay 112 USD for every 100 USD transferred to Atomic wallet). Are there cheaper ways to trade fiat to crypto?

Additionally, it is only half of the story. 

Atomic does not allow to transfer crypto to fiat and send back to bank account. To accomplish this I need to create another account in currency exchange like Bitstamp or Coinbase and verify it with some documents. Then I can trade crypto to USD and finally back to bank account. I did not accomplish this step so I don't know what are the costs of transferring back to bank account.

Apart of this, I've found that some trading platforms, like Ledger Live require particular devices to be bought to be able to trade crypto. Making it useless for other wallet owners.

My question
- what are the most convenient (ideally one platform) and cost efficient ways of trading crypto for fiat and back?

I assume that at the moment there is no single platform that does this but at least two accounts are needed to trade. In this case what are best ones according to cost efficiency and market accessibility?
Depending on where you live there are different options. I would suggest, if in the US, to go with one of the larger platforms like Kraken.com, or CoinBase.com. In these systems you can wire funds (Kraken) or attach to a bank account to purchase currency. 

In my experience, CoinBase will be your training wheels. It's hard to see what you're buying/selling as the actual transaction occurs automatically when you click the button. What you see is not what you'll get (unless that changed in the last week). However it is very easy to use.

Kraken will require more verification for additional tiers (work with more value). But you can control the trading. You can set buy/sell limits which means you won't get 1 penny less than what you told it. They have tons of additional trading options if you want to get more advanced as well. 

Final note, Kraken supports many more crypto currency options and bought cryptowat.ch over a year ago for a nice live feed of prices across multiple platforms.

Hope this helps you get started!

Edit: I'm not here to judge intentions or viability. The question was  "what can i use". Any assumption (including commentary on the current market, political, legal, etc) other than "I'm simply answering the question" would be incorrect.