Hello and welcome to the Forum!
You can select any of the trusted brokers we have on the website, and as well for crypto trading, I use Pepperstone.
Please, have a look at the lecture where I explain the Formula. I show step by step how it is calculated. The lots increase because it needs to cover the loss from the previous opposite trade.
Also, have a look at the Assignment attached. It will help you learn how to calculate it. If you still can not figure it out, let me know and I will send you the further calculations and lots.
It is good to have higher leverage so it can handle more trades if necessary.
The type of account doesn’t really matter. It is according to your preferences and the options in the broker.