I had the infant car seat and am glad that I did when she was little. It made going to the store and other places much easier, unless you plan to always wear them. There were times though that I just wanted her to be in her seat, like when we would go out to eat, or go to the Dr's office or something. Plus, when I would be gone from the house all day, it was nice to have a place to put her if she needed to sleep that was safe. By 8 months when Devin was sitting on her own for a few months and getting too heavy to carry in the infant car seat, we moved her to a convertible one. Sorry, I am not much help. If I had to do it all over again from scratch, I would probably still get an infant car seat again. The
Graco Snugride had the best safety ratings when I bought ours and wasn't very expensive compared to others. We avoided the combination packages, and opted for a
stroller frame which I bet you could buy used for really cheap. I LOVED mine and am glad I didn't spend a lot on it and got a nice stroller later when I knew what I wanted.
ETA: I really liked the stroller frame. It was very light weight, moved around nicely and didn't take up a ton of room in my car. I know you could find a used one inexpensively somewhere.