There are many chess openings you can play. Some of them are dubious and not played at top level chess. Just play what grandmasters play. But first you have to learn which openings exist.
What is the best Opening in Chess?
There is no such thing as BEST OPENING. What is best for you? This is the question. Best is what you know best and can handle best. Try to become an expert in some selected opening systems.
However, stay away from dubious chess openings that are played by amateur players.
Why wasting time learning some junk openings when you can learn some sound chess openings played by chess grandmasters worldwide?
First get an overview about all popular chess openings that are played nowadays in chess tournaments and chess matches worldwide.
Avoid the dubious openings to avoid wasting time and select some sound openings like Sicilian Defense (not the Dragon Variation), Ruy Lopez, Slav Defense, Queens Indian Defense, Kings Indian Defense, Nimzo-Indian Defense, Queens Gambit etc.
What kind of Chess Player are you?
First of all decide what will be the first move when you have the white pieces. Then start from there.
Are you a 1.e4 player? Are you a 1.d4 player? Are you a 1.c4 player?
What is the difference?
The 1.e4 player likes aggressive opening lines and is able to handle them without losing his nerves. If you are a beginner or a young player then I would recommend that you play first move 1.e4.
This is the most effective way to study chess principles in action because the game is fast-moving. One big mistake and you are done. If you don’t follow chess principles you are done very quickly or your opponent is done quickly. You will win faster if your opponent is violating any principles when you play 1.e4.
If you are older and have not the nerves to get into aggressive lines right from the start of the game then start with 1.d4. But stick to it for the rest of your life. If you switch openings all the time you never ever become any good, unless you are a genius.
If you don’t like to have any confrontation at all for the first ten moves or so start with first move 1.c4 or 1.Nf3. You will get a very quiet positional game. But don’t fall asleep.
If you play like this you need a lot of patience and have to immerse yourself in deep positional chess where you accumulate small positional advantages over hours of play, until you reach a winning position. Do you really want to do this to yourself?
Many lines are just to boring when you start with 1.c4. I recommend you start with 1.d4 and stick with it. Because there is a lot to learn as you have to study all defenses that Black can play. This will take a life time.