the GTX760 has a moderate max TDP of 170W.
the recommended PSU for that graphics card is 500W, just be sure your PSU is not a generic one.
Use only good branded certified PSUs to do overclocking activities.
depending on OC intencity, you will need some extra Watts and extra cooling,(OC produces more heat), but I dont recommend you to OC cause as you just said(I'm kind of a noob with PC's.), So you must learn how to do it first, OC activities have some risk, and tend to reduce components lifespan.
You can do a lot of damage to your rig doing OC with improper configurations.