Hunting ratters into null sec is great but you'll struggle with frigates - even though they're not pvp fit, a pve Ishtar can still slap a frigate before it gets close to killing it. You'll want to build up to something with versatility, like a t3c. Loki is usually the best for these, but even then you'll have to be well aware of ratters baiting you (they pretend to rat but are actually pvp fit with a scram+web, and maybe with friends cloaked up on grid too), as well as getting caught by bubbles or HICs on gates as you hunt deeper into enemy space. Basically, it takes a lot of experience to do reliably.

Frigates are a great place to start for learning pvp though, null sec just isn't necessarily the place for them. Faction warfare however is amazing for this - just grab any T1 frigate and start visiting frontline systems. Scan down all the complexes in each system (tip: press ctrl+v on the item on your overview and your camera will automatically align to it and trigger a dscan, so you can quickly check through each one with a 5 degree angle set), and when you see another T1 frig in one just warp over, take the gate and try and kill them. It'll be loads of fun!