[LordArioch]

I understand why blood magic and underwater nations aren't good for new players, but there's nothing wrong with death magic itself, but just some themes that use it.
Nations to avoid:
Ermor (Any theme, Default is most normal if you must play Ermor)
Pangea default theme
Pangea Carrion Woods
Mictlan
Ctis Miasma
Ctis Desert Tombs
R'yleh
Atlantis
Marignon Diabloical Faith
Caelum any theme

None of these are probably a great choice for a nation to learn the game with. I might have left something out, but all of these have some unique and possibly problematic features.

Also for prophet choice at least, my general rule is a decision based on the nation's best priest level.
Level 2 priest: Commander becomes prophet for sermon of courage
Level 3 priest: Priest becomes prophet for fanaticism
Level 4 priest: Scout becomes prophet. Smite is nice but my lvl 4 priests are usually busy casting fanaticism anyway. The scout can spread dominion outside of your provinces and stealth preach.