Egypt near the med is always a pretty good choice. Large pop, stable, and more importantly is strong enough to not have any major threats near it for most if not the whole game. Outside of the initial Diadochi wars, you don't even need to expand, but if you choose to your neightbors are pushovers. Southern Egypt, Nubia, Aksum, and Arabia are all great places to try out founding cities and playing around with pops.
Stepping away from the med, you have the Bosporan Kingdom. Despite they're size they're defintely the most powerful nation there and it's easy to make a few early allies with your fellow Greek neighbors. After some initial blobbing (which is somewhat mandatory in order to get your pop numbers up), it's a good location to try out colonization, city founding, and slave raiding (mainly to boost pop numbers and then shuffle them around to grow your cities). There's lots of navigable rivers up there which make for some great natural borders, and they're fairly out of the way so it's easy to stay isolated and work on your country.
After that, you could try Maurya. They're basically just the Egypt of the East. You're strong enough so that you'll never really need to worry about anyone, and even if you don't expand at all you'll probably still be the biggest guy around there. This will give you some good experience with managing a massive empire, but still has plenty of rural areas that you can develp, especially places along the coast or near your rivers.
Finally you have Bactria. They're probably a bit more challenging since you have a lot of unhappy pops at the start and some big neighbors, but they share a lot of the good qualities of other nations here. High pop base, some colonization, urbanizing rural areas, etc. If you expand into the himalayas you can get a taste of food management, and the steppe is great for urbanizing.