Also my recent short campaign guide:
My first choices that I played were Spain, England, Russia. I tried to play all factions with a short campaign before tackling the longer campaigns. This might work for you also.
Regarding mods and features -- if you do not already own Kingdoms, this would be my first suggestion. The mods within it are new skins and you get boiling oil as well as some fort action. The next step for me was the Retrofit Mod which adds in the Kingdoms .exe into the vanilla M2TW as well as some rebalancing of the unit stats.
Good luck and keep us informed.
Regards,
VP