As a beginner, focus on a maximum of one to two stocks during a session. Tracking and finding opportunities is easier with just a few stocks. Recently, it has become increasingly common to be able to trade fractional shares, so you can specify specific, smaller dollar amounts you wish to invest.
That means if Amazon shares are trading at $3,400, many brokers will now let you purchase a fractional share for an amount that can be as low as $25, or less than 1% of a full Amazon share.