USA is easy, only problem is "Wickedness must be stamped out."
France is another good, easy option. Try to recreate Napoleon's Empire!
Brazil is similar to the USA, albeit weaker.
Russia is easy, but involves 50+ years of buildup before you start flexing your muscle on the world stage. in the meantime, try to win the Great Game!
Don't play:
Austria: populous and has plenty of raw materials, but it is in a bad position in Europe and thus has a foreign policy nightmare to confront. The rising nationalism of your subjects doesn't help matters.
Netherlands: used to be a good newbie nation, but nerfed to crap with HoD colonization mechanics.
Belgium: Ditto.
Ottoman Empire: same issues as Austria.
British Empire: strongest start, but by endgame, it's usually weaker than the USA and Germany. Victoria, despite the name, is pretty much the story of Prussia, rising up onto the world stage, taking its place in the sun against Britain, France, Austria, etc, and then in turn having to confront the usurper that is the USA. The British Empire is basically the villain of the story, seeking to contain and stymie its enemies. This can be fun for experienced players building a Cape-to-Singapore railway and taking land from France. But it might be boring for newbies, and discouraging if they fall from #1.
Greece: I know it's everyone's fantasy to rebuild the Byzantine Empire. And it
can be done (shameless plug, but this took me the better part of a day to accomplish, so I deserve to be happy about it. It's called the "Byzantine Empire" in Vanilla, the "Greek Empire" in Vickymod). But it's an exercise best left to experienced players. You'll have to go on ahistorical adventures to Cameroon and Malaysia (Being too ahistorical grinds my gears, tbh), and that bothers me. Also, you'll have to go through an ungodly amount of reloads, because challenging the Ottoman Empire is no mean feat, and everything needs to go perfectly for you to come out on top.