I use a connecta. It is from 3.5kg and up. It is good for taking the weight off your shoulders and your baby's legs form the 'm' shape they are supposed to, but I do find I have to wriggle and jiggle DD to get her just right. However, it takes up virtually no space and I have a nice breathable one so we don't get all sweaty being squashed up together!
Do you have a sling library near you? Different people find different slings comfortable but there are lots of sling libraries and sling meets around the country, you might be able to try some before buying. There's also a big second hand market and several Facebook groups- babywearing FSOT has second hand carriers & wraps for sale
Ive got a Rose and Rebellion which is nice and comfy. In fact I just bought a 2nd one. I'm peetty sure they're from 3 months up though with good head control. Having said that it's long enough in the body that my 3 month olds' heads/necks are supported by the carrier. A mei tai is good from newborn and having just bought one they are just as easy to use as a ssc just takes a minute longer to tie the straps. Mine is a cheapy from mnsdesigns on ebay but very well made, good padding and comfy.
I had a Moby for DC1 but got a Manduca for DC2 as wanted something easier to get on/off. I totally love it! For me the critical part is you can cross the straps over your back, rather than wearing them like a rucksack so it is so comfy. Can't recommend it enough.