Not sure what you mean by calculation of pip and trade size but a few pointers, let me know if I touch on things that in that area.
Gold
Most traded gold contract is the Comex gold, on the Globex platform(CME) you can check the contract specifications under
www.cmegroup.comThe margin requirement is around 4000 dollars per contract, this is when trading with a clearing firm, when using brokers say the usual guys, AVa fx, Iron fx etc, you just need to put capital, try to put at least 3k dollars to trade well.
The pip value/tick is 10 dollars, but if trading with the retail brokers you can use mircolots so 0.1 lot is 1 dollar. The key in trading gold is two things, data driven(get to know what moves gold and when so that you dont get caught out) the second is technicals. Brush up on them before trading, not during
In terms of trade size there is something called money management and risk management. Your account determines what size to use, previous trades etc. I would suggest you use a dummy account to practise, try doubling your account like twice before placing real cash.
The above will help you understand about size, there are a couple of other things that you shall learn, when to be greedy and when to be fearful, how to handle losses, keeping a cool mind etc.
Parting shot-Trading is not everyone's cup of tea, you shall loose money before you make. If you have been trading before then this is a concept that you know of already.
Cheers