I started with half dollars .. learned how to coin roll then palming coins, and started to learn Eric Jones and David stone routine. Hope it helps.

Get yourself 4-5 kennedy halves, and dollars. As others have said, you will need to experiment with sizing, palming, other slights, etc. Also, you may find you like using halves for "in the hands" work and dollars for table work, for example. Or you prefer to do certain slights with different coins. The most important thing when starting out is experimentation without blowing a ton of money, no pun intended.

I'm going to go a little against the grain here and suggest: choose coins YOU like, that interest you.

If you know you want to follow recommendations to try half dollar size, you can find all kinds of coins you like in the correct dimensions. And there's really margin for give and take on the size.

Certainly think about presentations you'd like to pursue and compatibility of coins for presentation. You can have a lot of fun looking around for coins that will fit a presentation style, and that will lead to myriad ideas YOU like for expanding on that.

I had lots of advice to go with clad Kennedys, but I'm from Canada for one, and the idea just did not appeal to me. I knew there was no way, even when David Roth suggested them, to my face. Of course, David is flexible and versatile and his advice was merely a suggestion and not a direction. Would have been a nearly total waste for me to go with those coins and I knew it. So, I went with what I like.

Poker chips are a great place to start practicing.
They are cheap, don't make a lot of noise when you drop it and you don't have to be a afraid to lose them.

Yes. But avoid the Tango E$&?!$d!d S$@!l set. Not great to work with. Much prefer coins.

Clads are slippery, worthless imo slip and slide.
silver is sticky and you can work them better than clad.
silver is cheap. once you work silver the clads get spent.

Agreed!

It depends on your hand size and anticipated performance venue to some extent. If your going to do parlor, dollar size coins are better because they are easier to see. For me, when doing close-up, I like halves or sometimes quarters because my audience can hold them comfortably. Someone with small hands will have a harder time wrapping their fingers around a dollar coin. Since your in the US, I'd probably suggest starting off with a half dollar size coin. I like the feel of silver but clad are fine for starting out. When you carry coins in your pocket all the time so you can practice it hurts a lot less when a clad coin goes missing. If you end up doing a lot of coin work, over time you'll want to be proficient with many size coins.

I'd recommend starting with Half-dollars, as they are visible enough and not too big or small, but as said above play around with different coin sizes, even the small ones. A time will come when either a certain trick requires it, or you'll have to make do with what's available.