Do you have any access to an ostomy nurse?
Getting samples and trying different brands as suggested is a start, but there are so many variables, it will take you quite a bit of trial and error to figure it all out. Even one or two visits with an ostomy nurse will give you a good foundation and help you get started.
People here are very knowledgeable and they will chime in with great advice, but nothing is as good as an experienced eye on site.
FWIW, I have used both Hollister and Coloplast successfully. Both have pluses and minuses, but you need to figure out your leak issues first. Assuming your fundamentals are solid, a different brand may work better. But being new myself, I can say that many initial problems I had were more about my technique than the appliance.
In the meantime, a few things that gave me trouble:
1) It's best to clean the skin with only water. If you use soap, make sure it contains no lotions and clean the skin well with water to remove all soap. Anything left on the skin can cause the appliance to loosen and leak.
2) Make sure the skin is very dry. If you use barrier wipes, the liquid must dry completely. Some people use hair dryers on a low setting or a small fan. I had a very bad experience with barrier cream that just didn't dry well, so now I use the wipes or nothing.
3) Barrier rings (wax-like rings that go under the appliance) can help prevent leaks. If using these, make sure to warm them well so they stick better to the skin. I was taught to press them with my fingers after applying to the skin.
4) While learning, I recommend flange extenders. These are semi-circular pieces that are designed to go around the outside edge of your flange. Depending on the brand, two or three extenders will cover the entire outside edge. I found these invaluable for helping to delay a leak. They gave me more time to spot a problem before it became a mess. You may or may not need these permanently, but I consider them a great hack while learning.
5) Make sure the flange is sitting flush against flat skin. Any scars, skin folds, etc., will provide a weak spot for a leak. There are ways to deal with these problems, but it would be difficult to assist without more detail. This is where an ostomy nurse would be most helpful.