For ease of use you can't beat a pouch sling - like a Hot sling (though there's lots of brands out there now that are like that). It won't last as long as some other kinds of slings, but it is very easy to use. And you can always sell it when you're done to fund the purchase of the next sling.
A wrap is the most flexible b/c it has the most different ways to wear it. But it has a bit of a learning curve. Moby is the popular name there, but again, lots of other brands exist or there are patterns/suggestion online for making your own which wouldn't be very expensive at all. Ring slings have some flexibility and like wraps can be used longer. There's tons of different brands to buy from out there and lots of patterns for making your own.
Slingriders and all other slings like them have been recalled b/c of the risk of suffocation. Babies are put in an awkward position with those bag like slings, so it's actually a good thing that your child didn't like it.
She was likely uncomfortable.
And there's other carriers, too, that I don't know a whole lot about, but some don't work well for newborns. thebabywearer is an awesome site!