Keep it simple, keep it slow - higher rated players will tell you that you should study NO openings. I don't think this is quite realistic or fair - because opening knowledge is really all about learning how to get middlegames you are comfortable with, so you need to at least try to play some of the same moves in order to really understand the 'world' created by a particular opening system.
As white - pick a move. e4 and d4 are recommended, c4 is fine too (if you like quiet positions).
for e4:
Classical: Pick ONE and only ONE of these to study to about the tenth move - Ruy Lopez, Italian Game, Scotch Game.
Sicilian: Maybe start with the c3 (AKA Alapin) because it doesn't have the sheer volume of theoretical variations that you'll get from an open Sicilian. c3 controls black's options for response.
Caro Kann and French: I'll lump them because the pawn structures are similar - they are definitely NOT the same though. You'll either want to play an exchange, an advanced, or a classical. JUST PICK ONE
Scandanavian: I don't know the lines, but it will come up, so look at it and pick ONE variation that will be 'yours'
Alekhine: Just chase the knight, play d4, chase the knight again, and let the game flow naturally. Alekhine is fluid, don't bother preparing your lines too deeply.
for d4:
Classical: Just play the Queen's Gambit - it's the 'best by test' (so to speak)...London is tried and sworn by, but just play the QG; you'll thank yourself.
King's Indian defense: There's a consistent development pattern for all the variations - play it, mind your center, and attack on the queen side, and you'll be OK.
Nimzo Indian: Mind the e4 square, choose how you're going to recapture the knight if it's taken (the queen or the b pawn), and look out for the counterattack with c5.
Grunfeld: Look at example games....this is the hardest thing you'll face because it is highly tactical and hard to predict - luckily it's also rare.
For c4: Look at the symmetrical English with ...c5 (which is an exact mirror) and look at the Sicilian from black's perspective to deal with ...e5 (which makes your position a backward Sicilian)
For BLACK - pick an e4 opening and a d4 opening and learn JUST THAT ONE - don't go crazy building a giant repetoire.
In general: DO NOT memorize moves and try to learn everything all at once. You will forget your theory, get it all tangled up, walk 13 moves in to a main line, forget the 14th, and be killed. Save yourself the heartache. What you need is to think about these positions in terms of a pattern of development and a pawn structure because, while individual moves change, those concrete features will be somewhat reusable from one game to the next (Example: the bishop in Queen's gambit almost always goes to g5...if you put it on g5 - whether or not theory says it's the right move - you've almost definitely helped your position).
Think of theory as a magical chess Yoda: It suggests moves to you, but you are the one who must play them, so learn the moves, but, more importantly, learn WHY you're playing them.
All the best!
My repertoire so far consists of the following:
White:
Black:
I've been doing some reading around and it seems the consensus is rather than learn variations and theory, a beginner should focus on learning just a few openings and defences for 1. d4 and 1. e4 while obtaining a good practical knowledge of the resulting positions.
With that in mind, I can already see that I lack any 1. e4 openings as white and I could do with another for 1. d4 (as apparently the Reti can turn into just about anything, so I don't count it as a separate opening). As for black, I feel pretty comfortable with what I use already but still, I could do with more variety.
I should note that I have a difficult time remembering strings upon strings of moves (a difficulty that I'm hoping time and experience will erode) - instead I rely on my own OTB analysis skills and knowledge of chess principles to evaluate the position at hand and decide what needs to be done. So I'd prefer suggestions that don't require me to learn endless tracts of theory and of course are relatively easy for beginners to play well. After all, I'm a uni student at the moment and don't have time to spare to analyze openings to death.
Cheers :)