They say that beginners should learn
1. e4 as White first, and the "natural" response
1... e5 as Black. But I think it's a matter of personal taste.
Usually for beginners the easiest openings are those that simply stick to the basic principles: pieces development, occupation of the center, King safety, tempo.
In my opinion, at this stage you should avoid openings having somewhat "complicated" strategic ideas, such as 1) "control of the center without occupying it", or 2) "induce pawn advances and center occupation in order to attack it later", or also 3) "lose tempo to gain positional compensation". To me, it's important to grasp the basic principles before you go and break them, even if the resulting openings are sound.
This rules out most of the Indian Defences against
1. d4, as they fall in both categories 1 and 2. Same goes for the Sicilian against
1. e4 as its main purpose is to avoid White having an
e4 d4 pawn duo in the center, thus falling into category 1 (center control without occupation). Many other openings fall into these categories and should be avoided, such as the Scandinavian Defence (cat. 3), the Alekhine Defence (2), the English (1), the Dutch (1), and all the "unusual" openings for Black and White (Bird Opening, Indian Attack, Lasker Opening, etc.).
Note that this doesn't mean the opening I just mentioned are bad: they are sound, and some of them are really a lethal weapon if you can handle them well (I'm thinking about the Sicilian and most of the Indian Defences, for example). But you should first try the "most basic" ones, before you go and dig deep into these.
To me, the most basic openings to study as a beginner are the "symmetric" openings, thus
1. e4 e5 and
1. d4 d5, as they stick to the basic principles of the openings.
1. e4 e5 I recommend
- Italian Game, classical variation
2. Nf3 Nc6 3. Bc4 Bc5
- Italian Game, Two Knight Defence
2. Nf3 Nc6 3. Bc4 Nf6
- Four Knights Game
2. Nf3 Nc6 3. Nc3 Nf6
- Ruy Lopez
2. Nf3 Kc6 3. Bb5
1. d4 d5:
- Queen's Gambit Declined
2. c4 e6
- Slav Defence
2. c4 c6
Of course if you are a beginner you shouldn't go too deep into these lines, but just have an overall grasp of the resulting positions and the ideas behind them.