It's always mindful to keep your leverage low initially which exposes you to less risk as a beginner because with leverage comes the responsibility to win and initially as a budding trader I personally feel low leverage exposes you to lower risk.
In my opinion beginners should start with small leverage. As with leverage comes responsibility and risk.
when you have most powerful analyzing risk management only in that time you are able to bring good amount of profit by using any kind of leverage ratio.
the beginners level should not use the leverage at the first stage of trading, this is really a high risky issue
I don't think there is the best leverage amount, you can always set your risk using lot size. Leverage just determines your ability to open position that exceeds your own capital but it still has a great deal of flexibility.
when there is any good money management you are able to bring a good amount of money from there by using any kind of leverage ratio.
I recommend newbie beginners to trade in demo accounts to understand more about the forex market and the trading methods, and for beginners that have demo experience and are looking for live trading experience, it is better to trade with a smaller leverage of 30:1 or even lower to avoid losses.
If you are prone to gambling and over trading then go with low leverage. High leverage in of itself isn't a risk but miss-use of it is.