Help on infant car seat?

Have yet to buy a infant car seat because not sure on which one? Had a Graco snugride with our first baby it snapped into the stroller. We then transitioned her into a Chicco convertible at 4 months that she still uses now and she just turned 3! I'm going to be using a ergobaby carrier this time around so I don't think we need a stroller right away. Just need help on the carrier? Or unless there is a nice travel system?