Investing Stocks
Watch the price charts and buy when the bar is low on the graph and then sell when the bar is high. Better traders make for a better success rate, which is where the real value of those 4-5 star traders comes into play.
Trading Stocks
With trading stocks you have the option of either buying the maximum of a specific stock, or buying a specific number of shares. To increase the maximum that you can buy you need to level up your Stock Trading License.
Bond & Artifact Trading Licenses
You will open up new categories of trade that you can exchange in when you purchase the bond and artifact trading licenses. They work the same way as stocks do so you need to check the price charts before you buy and sell.