You have to be able to make a decent start in a game of chess, or you risk being blown away by your opponent's better development. Knowing a few openings in a bit of detail is some insurance against traps and ideas that you haven't seen before.
So, here are some variations in common openings that you can -- and should -- learn. At each turn, try and learn not just what is the right move(s) but why that move is preferred.
[Event "?"]
[Site "?"]
[Date "2018.01.30"]
[Round "?"]
[White "Felix"]
[Black "Openings"]
[Result "*"]
[ECO "C54"]
[PlyCount "11"]
[EventDate "2018.??.??"]
1. e4 (1. d4 d5 2. c4 e6 {and one or other line:} 3. Nc3 Nf6 (3... c5 4. cxd5
exd5 5. Nf3 Nc6 6. g3) 4. Bg5 Be7 5. e3 O-O 6. Nf3 Nbd7) 1... e5 (1... e6 2. d4
d5 {and these lines:} 3. e5 (3. Nc3 Nf6 4. e5 (4. Bg5 Bb4) 4... Nfd7 5. Nf3 c5
6. dxc5 Nc6) (3. Nd2 Nf6 4. e5 Nfd7 5. Bd3 c5 6. c3 Nc6) 3... c5 4. c3 Nc6 5.
Nf3 Qb6 6. Be2 (6. Bd3 Bd7) (6. a3 c4)) 2. Nf3 Nc6 {and now the main lines of
one or other opening:} 3. Bc4 (3. d4 exd4 4. Nxd4 Nf6 (4... Bc5 5. Be3 Qf6 6.
c3 Nge7 7. Bc4 (7. Be2)) 5. Nc3 Bb4 6. Nxc6 bxc6 7. Bd3) (3. Bb5 a6 (3... Nf6
4. O-O (4. d3)) 4. Ba4 Nf6 5. O-O (5. d3)) 3... Bc5 (3... Nf6 4. Ng5 (4. d4
exd4 5. O-O Nxe4 (5... Bc5 6. e5 d5 7. Bb5 Ne4 8. Nxd4) 6. Re1 d5 7. Bxd5 Qxd5
8. Nc3 Qa5 9. Nxe4) 4... Bc5 (4... d5 5. exd5 Nxd5 (5... b5 6. Bxb5 (6. dxc6
bxc4) 6... Qxd5) 6. Nxf7)) 4. c3 (4. b4 Bxb4 5. c3 Ba5 6. d4) 4... Nf6 5. d4
exd4 6. cxd4 (6. O-O) (6. e5) *