When a trader first starts to trade there are many things to learn like:
1.   How to use the platform
2.   Which trading style I should use
3.   Which indicators should I use
4.   What time frames best meet my life schedule
5.   How much money should I trade with
6.   How much should I place on each trade
7.   How much of a loss should I take
There are many other things to consider when trading but the one I want to address here is how much money you should risk in the market at one time. Here is one formula of how to calculate the amount of money you may want to trade at any one time.
You should trade with no more than 5% of your account on any one trade. i.e. $2000 account x 5% = $100. Divide The 5% or in this case the $100 by $50, which is the amount of margin you will be using in a mini account. $100 divided by $50 gives you 2 lots per trade.
This is only a formula, be sure to trade on the side of caution.
An even better way is to take half of the money you have available for trading then use the above formula on only half of the available money to trade. In this example the available money to trade would be $4000. So you would have $2000 in an interest baring account. This money then becomes a safety net. And $2000 in your trading account. So if you only have half of your money in the trading account then you cannot be wiped out. By using this method lets you trade and still be around for more trades when you recover from wiping out the first half of you trading capital.
I have a friend that says this about new traders. “New traders should put half of their money in a saving account and write out a check to him for the other halfâ€. This way they will be money ahead. So if a trader uses the method in the above paragraph they can still trade and have money to trade again once they recover from the loss in the learning stage of their trading career.
Use caution and patience in your trading. Practice, learn from your mistakes, follow a trading system, and have fun.