As you level you will automatically learn certain spells and abilities which will help you become more powerful. However, to make sure you are as strong as you can be, you will need to allocate talent points as well as use rubies into your talent tree and talent grids. To access the talent tree and talent grids click the Talents button on the left tool bar, or simply press "N".
Sometimes spending talent points or rubies will simply give you a higher rank of a spell or ability you already know. However, sometimes you will be able to learn entirely new spells or abilities. Spells and abilities you have already learned can be found in your Spellbook by clicking the Spellbook button on the right tool bar or by pressing "P".