Keri,
From someone who is still considered a newbie! And this is JMHO-
I have been showing Shetlands for 3 years. My initial attraction was the Moderns! But I started out buying classics and two Modern Pleasures. Both my stallions can be shown MP. I have not bought a Modern yet, it takes a lot of work with a Modern.
First you have to understand the rules, which can be confusing until you go to a show and find someone that shows Moderns and you can ask questions. Then watch the classes. I finally understand I think to the point where I can buy one and show it half way decent, but I probably will wait until next year.
A ferrier that can shoe correctly- is most important. I don't know about most people, but during the show year, these ponies don't get to run and play like a normal MP or Classics can. They have the potential to throw a shoe to easy. And unless you can put it on yourself (not recommended) it is takes a lot of money for upkeep. Of course I am talking mostly about the show season.
Depending on how extensive you want to show - tack is another concern. The top ponies have full tail sets on most of the day. Depends on who is showing the horse and their preferences.
So what I guess I am saying, its not something to just jump into - I would go to as many shows that have the Modern's showing and absorb as much as you can. Ask questions.
Another thing you can do is visit some farms that specialize in Moderns. See how they are kept during the show season and then off season.
Tailers are necessary if you want to compete in Moderns, but not everyone has one. If your pony isn't used to having one - that could get interesting at a show. I don't have a tailer, I have some wonderful friends that attend shows that I hit that will help me. But my ponies aren't used to that so it is kind of interesting to see how they react.
I like my Modern Pleasure ponies, they are easier upkeep, take a light shoe that most ferriers can put on, if you want a shoe. They can still have turn out with these shoes, you don't have to worry so much about one being thrown. They are often just as flashy as a Modern. You can still dress them up with show halter, or bridle. They still need the ribbons. But they are a great starting place!
I don't want to be discouraging - I just want you to be aware of all the things needed to show these fine animals and some ideas to start you off with.