After fiddling with a few apps, I found Coinbase to be the best as far as UI.
Their charts are pretty
And you can search most coins (even unsupported ones) and get a lot of data and news about them through that app. This is also the app I connect to my bank account, NO OTHERS. It's one of the most legitimate apps to use in the US.
Any time I buy crypto, I use my USD and buy XLM with Coinbase.
After that, I transfer that XLM into Bitmart, which is the only app I use to BUY/SELL/TRADE with.
XLM has low transaction fees, and will keep Coinbase and the IRS from taxing you too crazy, since you're only really paying ridiculous capital gains tax on holds under a year. You won't be paying capital gains tax for trading on a platform like Bitmart, which doesn't accept USD and won't connect to your bank account (which also lowers their tax liability). So you can go CRAZY on there with the trading
Once you understand (use Google/Youtube) how to copy wallet addresses correctly and paste them where they need to be, to transfer your XLM into your Bitmart wallet, you then SELL all of that XLM for USDT. USDT is a stablecoin, virtually equivalent with the value of 1 USD.
So if you want to invest $300 into Shib, buy $300 of XLM on Coinbase.
Send that XLM to Bitmart.
SELL 100% of your XLM. (It will automatically be converted to USDT)
Think of USDT as a digital dollar.
You can now use that USDT to buy SHIB.
Once you get your investment strategy, etc all worked out and you're ready to sell, just reverse the process. SELL whatever amount of SHIB you'd like.
BUY XLM
Transfer that XLM to your Coinbase wallet.
And finally, SELL the XLM on Coinbase for cash.
Transfer the Cash to your bank account.
SKIP the instant transfer, the fees will be high.
Do the 1-3 business days confirmation transfer, it's free.
If done this way, your tax liability is only for the initial purchase and transferring of the XLM from and back to cash. Everything else in between, you've legally avoided Uncle Sam on
I'm sure they'll find a workaround in the next few years, but until then, this is the process I use.