Next you'll need to purchase Luna. I use newton.co because I live in Canada and my bank makes it very hard to purchase crypto.

The primary coins on Terra are $LUNA and $UST.

$LUNA is the primary coin, or currency, of the terra network. It fluctuates often as people purchase and speculate on the price.

$UST is a "stable coin" - basically a coin that is pegged to the US dollar to make it easy to buy into and sell off the network at a stable price.

If your plan is just to earn money off Terra Yields (currently 19.5%), you only need to purchase UST.

If you plan to invest in the ecosystem (speculate) + earn yield, you'll still need some UST to get started. In this case, your first step would be to buy a small amount of UST to fund transaction fees before purchasing LUNA.