New Kill Team Player - How to Get Started?

I'm a new Kill Team player. I've tried demos with the Angels of Death and had a lot of fun, especially using the Eliminator (the sniper). I'd like to buy my first Kill Team and was considering Ratlings, but many have advised against them; they say they should play Elite. I'd like some advice on a good team to start with, one from the Imperium that uses firearms more. I already own several Kaserkin models because I play Imperial Guard in 40K. I'm open to any suggestions, thanks.