I am giving a list of cheaper seats because I know not everyone can afford the more expensive ones right off the bat, I bought a cheaper seat while waiting to get a higher weight seat.
If you REALLY want to save money get a convertible from birth that will last til 65lbs like the Truefit, its a one time cost of $180 MAX and you will only need to buy a booster for $20 7 years from birth.
Lower cost convertibles(from highest price to lowest)
Evenflo Triumph advance-Runs about $115-130 Rfs to 35lbs and FFs to 50lbs in harness, has tension knobs to change strap tightness, EPS foam, slide adjustment so no rethreading for harnesses
Safety 1st Avenue-Rfs to 35lbs, FF to 40lbs harnesses, has EPS foam, infant head support included, higher shell than the other 40lbs carseat so it can be RFed longer in height...about $85 at Kmart and Sears
Cosco Scenera-Rfs to 35lbs and 36 inches, FFs to 40lbs, great narrow seat, no EPS foam, no bells and whistles but comes in boys and girls colors and just as safe...it doesn't RF long or harness long but its a great backup and a cheaper seat while waiting to be able to buy a most expensive on...runs from $35-60 brandnew
heres my son RFing in it around 20 months
heres a girl one
Forward facing only boosters with straps
Evenflo chase-only used from 22-40lbs, but if you must move a child so a baby can use the convertible its a great spare if you can't get the next seat I mention..runs about $80..I own one myself, though have no pics in it
Apex 65- alternative to the Nautilus if you have high back seat or a good headrest, harnessed 22-65lbs and then becomes a booster. Big lots has it for $85 or albeebaby has it for under $100, has eps foam, adjustable headrest, padded toddler insert(though I recommend Rfing toddlers)
Evenflo Maestro-BEST alternative to the Graco Nautilus, carried in store and online at Sears and at Amazon.com. Harness straps are HIGH, much higher thanthe Apex 65, it only harnesses to 50lbs but most kids will not make it 65lbs in a harness because of height. This makes a decent booster and most harness to booster seats do not.