I can tell you how I do it, but I am not certain if it is the best way, but so far it works.

I use coinbase app on my phone to convert dollars into either BTC/LTC/ETH, then I either send it to my Exodus app on my computer, or to bittrex depending on what I am planning to do with it. My first transactions were simply about acquiring BTC but soon I learned how to make money with it. I put in a few hundred dollars and it has since more than doubled, and I am getting more comfortable about my trades and how I plan them. It is different for everyone but this is how I did it. I probably don't need to add money anymore, I can pretty much move it around and grow it. Of course, adding is always helpful. I don't put all my eggs in one basket either. In fact I have used 20+ baskets so far. (different alt coins). Hope that helps.