So, how to create a perfect Forex trading system?

First of all, you need to make sure your trading system fits your trading personality; otherwise you will find it hard to follow it. Every trader has different needs and goals, thus there is no system that perfectly fits all traders. You need to make your own research on various trading styles and technical indicators until you find a concept that perfectly works for you. Make sure you know the nature of whatever technical indicator used.
Secondly, incorporate price action into your system. So you only take long signals if the price behavior tells you the market wants to go up, and short signals if the market gives you indication that it will go down.
Third, and most importantly, you need to have the discipline to follow your Forex trading system rigorously. Try it first on a demo account, then move on to a small account and finally when feeling comfortably and being consistent profitable apply your system in a regular account.