Do you have any sling libraries in your area? If you can get to a library or trial session, I would definitely recommend it! My local library also do personal consultations which I found really useful. It was about £15 for an hour consultation which was great, I could ask as many questions as I wanted, try as many different styles as I could and take as long as I needed to make sure I could use the carriers correctly.
Some of them do trials by post as well. I have tried various slings/carriers with my LO. I have tried stretchy wrap, boba 3g, wompat, ring sling, hippy seat and a Scootababy. All have had their plus points and down sides. Ring slings are good but I personally struggle with them and dont really like them. I liked the boba 3g and I loved my Wompat for front carries. I am currently using a Scootababy which is working well as my lg really loves being hip carried. Its worth bearing in mind that most well known carriers hold their value and can be sold on if they dont quite work for you