Hi Clark welcome to the forum. Judging from the information you have given, I have come up with a few advice that I think might help.
Ok firstly, I get the impression that you do quite well in PES3. In that game, the difference is that it tolerates the running game. You used to be able to dribble the ball a lot better in PES3 and that might be the reason that you do well in that game. Ok although it is still possible to dribble with great effectiveness in PES6 but long gone are the days that Henry bolts past 5 defenders and puts it through the goals.. To do better in the later games in the series, you would need to run less and pass more. Don't use the R1 unless you are in open space. Don't hesitate to pass back to keep posession of the ball. Do long short passes by keeping the x down, this is good because it would bypass the closer team mate in the same direction (PES3 didn't have this type of passes as far as I know), and don't be afraid to do through balls straight in front towards the goal and make your strikers win the ball by outrunning the defenders (This also was not an option for PES3 as the through balls were no where near as damaging). You are right about practice makes perfect, keep practicing on what I've just mentioned and I think your game will improve quickly.
Secondly, I believe it is best for you to keep practicing on the highest level to improve quickly. I know that 3 star AI are very good at what they do and are quite efficient as well. But you should improve a lot quicker if you practice on 5 or even 6 star levels. If you are quite competitive on 3 stars. It should take you about a month to become competitive on 5 stars if you continuously play on that, and you will find it a lot more satisfying experience when you win a grinding game against the 5 star level. You can start by playing against weaker teams, you should find it wouldn't be a huge difference to playing against top teams in 3 stars.
Thirdly, regarding balooning shots, I find that anytime when you are within 30 yards of the goals, about a third of the gauge is about all you will ever need. As long as the shooter is well balanced, facing the goals and not being pushed by defenders, he will put in a decent and very powerful kick that's on target. and inside the box, sometimes I tap shoot very quickly and get as little as one tenth of the gauge, again the balance of the player is important, and with a bit of direction on the shot, he should put out a kick that is quite powerful and should whiz past the keeper before he even reacts. Do practice this in practice mode first and you'll know what I mean soon.
Fourthly, defense is often overlooked but it is so important to be patient in defense! Don't always be tempted to rush towards or double team the ball carrier, especially for defenders. Be patient, play your position, and steal the ball when the ball is exposed, Or intercept when your opponent does a bad pass. Also I think you don't need to use R1 unless your defender is behind and chasing the ball carrier, not using R1 as often will surprisingly get you a lot of steals and practically no fouls as your defender is on his toes, so to speak.
Ok Clark I hope I have helped you. Now it's all up to you now to practice and practice!! Do let me know if your game improves soon!!
