Newbie come lately?

[Kobal2]

Lanka and Hinnom/Ashdod/Gath are retardedly good. Tir Na Nog and Eriu, not so much

I wouldn't worry about sucking too badly in MP - there are quite a few newb games going on at any given time, and everyone sucks as badly as you probably will at first.
I enjoy the Six Lands map to try out strategies and gauge expansion tactics myself. As for good eras/noob nations, I think the Middle Age is the one with the fewest gimmicky/advanced mechanisms. EA has too much magic going on (not to mention supertough blessed units who might crush you if you don't prepare for them, while the LA often involves a lot of Blood Magic which takes some getting used to.
Try something like MA Arcoscephale with an imprisoned Oracle+good scales, or Man with a rainbow pretender - both are pretty vanilla while being decent enough against the AI.

Also, the wiki is your friend once you've got the manual memorized and realize there's still a ton of stuff you don't know.