There is no set page count for how long a feature screenplay should be, but generally speaking, your spec scripts should be between 110 and 120 pages.
The rule of thumb with screenplays is that one page equals one minute of screen time. Of course, this is not an exact science, nor do all movies run between 110 and 120 minutes, but as a novice, keeping your screenplays in this range will help give them a more professional feel.
As you become more established, you will have more freedom to bend the rules.