Most improvement at amateur/beginner level comes from playing long games (1-2 hours per game) and doing tactics. So, it seems that no time should be wasted on openings. However, that's not exactly accurate, as you shouldn't do much thinking on the first 4-5 moves. Besides, no knowledge at all about openings may lead to bad positions too early, e.g., in the Danish Gambit, King's Gambit, Petroff Defense, and some others. It's okay at beginner level to think on the first 4-5 moves but having no idea about the plans behind specific opening moves and trying to rediscover them is wasting time. Therefore learning some basics won't hurt, and there are good textbooks on openings for casual and beginner players, e.g. Openings by Seirawan, Chess Openings: Traps and Zaps by Pandolfini. You don't need most of the openings there - just some basic ideas and moves you run into or that appeal to you. You shouldn't study more than 10-20% in said books. You definitely don't need long move sequences at beginner level and these books won't provide them teaching you mainly ideas and plans. However, 80-90% of your time should be spent on doing tactics and playing long games - you should prioritize that if you want to improve fast. Only the remainder 10-20% you can spend on openings and some fun with blitz but the latter is a very bad idea to improve. Nobody became a grandmaster by playing bullet/blitz games - they did it by playing long classical time controls.
There are a lot of good books on tactics for beginners , e.g., Chess Tactics for Champions by Susan Polgar, Tactics by Seirawan, etc. (said books are for beginner but not for total beginners!) These should be your priority, not fast games. And you should be able to solve at least 2/3 of problems, otherwise you are just guessing and not calculating lines properly. Spend 40-50% of your time on tactics. Do them carefully and calculate lines properly. In the beginning, it should be just 2-3 move tactics and several minutes of thinking but you still have to mentally picture possible counterplay to your solutions. Make sure to check your solutions at the back of your textbook. Then take another book on tactics. Later on you can re-solve the textbook you solved, say, a year ago. It will help too. Eventually, you should increase the depth of calculations to 3-4 moves ahead and beyond and start doing more difficult puzzles. They will take longer to solve, say, 10 minutes per puzzle and that's when real progress kicks in. However don't try to leapfrog simple 2-3 moves puzzles. Make sure you meticulously solved (not guessed through) at least a thousand of them (not online puzzles!).
You should also play a lot of classical games (1-2 hours per game) in parallel with solving tactics if you want to improve fast. Doing puzzles alone is not enough. Invest at least 40-50% of time into long games. You can play them vs a computer, e.g. inexpensive phone/tablet app: Shredder. Just set the level (your Elo) and off you go. Play without time controls so that Shredder replies instantly. Do not rush. It's dozens of long classical games before you improve significantly. Don't spend less than 1-2 hours per game, otherwise you are not playing classical control games and not improving much. It must be mentioned that chess programs, especially at low levels calculate Elo too roughly. They tend to show higher Elo (by 100-300 points at low levels). What's more, chess programs usually don't adjust Elo for fast time controls. Whereas human quality of blitz is 600-700 below that of a classical game, most programs play even a bullet game with the same precision and with the same simulated errors as if it were a two hour game! There's also a free beginner's program called Chess Titans for PC/laptop with no openings which won't trick you even on the very first 4-5 moves. At its highest level, Chess Titans is still weak at around Elo 1500 FIDE and you might reach that level of strength in a few months of proper training.
If you don't play long games and don't do serious tactics from textbooks and (and instead you play fast and do quick puzzles online), your improvement will be perhaps ten times slower versus practicing chess seriously. When and if you reach the strength of FIDE 1600-1700 Elo (that's not difficult to reach), openings become slightly more important. Advice: if you are a casual player, don't waste more than 10% of time on openings but it doesn't mean you have to think on your first moves or you don't need specific ideas and plans behind them. Far more important is not to waste a lot of time on blitz, i.e., openings are the lesser evil to fast improvement. Many amateurs play dozens of thousands of blitz and bullet games online, sometimes it's more games than professionals ever played. The upshot is such amateurs invested too much time; yet the level for the time invested is ridiculously low. All right, they are having fun but they learned almost zilch despite a gargantuan amount of games played and quick online puzzles solved (often guessed through, and not really properly solved as online puzzles don't ask for variations - you just need to make move after move). Many such players might be tempted to resort to cheating to achieve some improvement perhaps out of desperation or lack of progress. You don't want such temptations to happen to you in the long run. Also note that most online rapid time controls are actually blitz games. The standard FIDE rapid time control is 15 mins + 10 second increment (that's around 25 minutes per 60 moves, and actually in the past before the digital clocks, it was just 25 minutes). Once again, you should play much longer controls if you want to see improvement.