I would recommend starting as US, France or Sardinia Piemont. US is simple to start with in the first 10 game years, France is stable and has almost all options to play with while not overwhelming and S-P is a major country that is overseeable and comes with a strong potential ally (France).
Like every AGEOD game the setting is historically accurate, with the downfall that you shouldn't ovresteer altering it the way you want it.
Management of economics and population is paramount. Build merchant ships and trade with a lot of countries both, selling and buying.
Did anybody mention the AAR section yet?
Note that there are a lot of restricting rules for requesting land in peacedeals.
The MP community are (mostly
) nice guys who will teach you to play first, before they eat you up.