1)Moves & all rules
You might think that you have to learn openings because other people rated around 1000-1200 may know a couple.
Thing is, if you concentrate on basic opening principles you really don't need to study opening theory until you get to at least 1400-1500+.
Do yourself a massive favour & buy 2 books which are all you'll ever need until you reach 1500
Logical chess move by move
- Irving Chernev
Winning chess tactics
- Yasser Sierawan
Then send me the cheque in a year or so
For what it's worth, I always go with the Morra against 1...c5 & have an 80%+ win record with it in 25 games.
It's highly tactical though, incredibly sharp & if you miss a tactic you are history.
I would never recommend it to a novice because they may not understand the key moves & move order changes depending on the black defence. A piece sac on b5 or a seemingly random pawn push from e4-e5 may not make the slightest bit of sense to a beginner & that's just for starters...