Question: how many spells can a wizard learn per level?
Answer: Each time you gain a wizard level, you can add two wizard spells of your choice to your spellbook. So, assuming you have a 16 Int, a third level Wizard can prepare 6 spells (3 int mod + 3 level), and your spellbook should contain 10 spells, probably 8 1st level and 2 2nd level.