If you trade Gold with fix lot, I prepared for you a simple manual how to calculate the best lot size for your XAUUSD trading account.
Step 1
Find at least the last 10 trades that you took on Gold.
Step 2
Measure stop losses of all these trades in pips
Step 3
Find the trade with the biggest stop loss
In our example, the biggest stop loss is 680 pips
Step 4
Open position size calculator for XAUUSD
Step 5
Input your account size, 1,5% as the risk ratio.
In "stop loss in pips" field, write down the pip value of your biggest stop loss - 680 pips in our example.
Press, calculate.
For our example, the best lot size for Gold will be 0.22.
The idea is that your maximum loss should not exceed 1,5% of your account balance, while the average loss will be around 1%.