Put some vids up of yoru gameplay if you want actual help. Its the only way, otherwise you are just getting generic help which may or may not relate to what your issue actually is.

There is no single best way to finish a 1 v 1. It depends on many factors, the angle of striker v goal, the time you have, which player you are using..........

I am not always great at 1 v 1, but if i am coming in from a sort of 45 degree angle, as in my striker is not within the width of the goal as he runs in, i tend to go for a power shot across the keeper. The exception is if i know my players weak foot is poor and the power shot would require him to use that. Then i will likely try finesse to the far bottom corner. Bit hard to explain without vids......

If i am running straight in on goal, i will either look for a sweaty pass, lob if the guy rushes the keeper or if i have time, move the ball before shooting (ball roll is best) to create an angle. Sometimes straight 1 v 1 a power or finesse will work, but keepers seem to save a lot of power attempts in that situation.

But yeah put up some vids of a few mins of your gameplay - I did this, was on 850 skill points, got loads of advice here, followed vids of others, got the right custom tactics and i am now at 1390 skill points (hardly amazing i realise, but its miles better than i was!)