Here would be some of the things I recommend if you want to go pro:
Gameplay: If your going for a team of 4, I would recommend practicing solid BR game play. Make sure you practice DAILY for at least 2-3 hours a day. Matchmaking may not always be at your skill level, so try to do some 1v1’s and such with your teammates, do clan battles etc. Get creative.
Teamwork: Teamwork is IMO, more valuable than personal skill,because you may all be extremely good, but if you all run around like a bunch of goofs, then your going to get nowhere.
Communication: Another very important factor, communicating with your teammates is essential. Knowing where your teammates are and when can be very helpful. Make sure all your teammates have a high quality mics (such as turtle beaches) , and that you are all clear with each other. Try learning some call outs, such as “One shot on my X” and others.
Diet, Health, Mental and Physical state and Sleep: This may sound silly but these are all very important. Making sure you get enough sleep at night is very important, being tired while trying to game is not going to help you out. This also may sound dumb, but is also true, being active while your being a professional gamer is important. Being active keeps your reflexes sharp, and your body of course healthy, staying on a healthy diet can contribute to this as well. Also,eating and drinking before a match can help your game play. I would suggest drinking something high in caffeine such as coke/pepsi or an energy drink.
Reflexes: Lastly, you should be strong on your reflexes and always be trying to improve them. Believe it or not, but there are actual workout equipment, for your hand and thumbs to improve your gaming skills. I don’t know what exactly its called, but people who play League of Legends professionally use it to keep their thumb and hand movements as fast as possible. Try playing other games as well when you practice,games that require faster use of your reflexes. COD would be an easy example, and most similar in gamestlye, but rock band blitz is actually a great game to play to improve your reflexes and hand eye coordination.
Hope this helps!