You need to get a handle on the leaks. As long as they are happening, you are going to have skin issues. If you have an ileostomy, it is even worse because of the frequency and liquid nature of the stool. Everyone above has given good advice. The biggest point, for me, is attaching to dry skin and making sure the adhesive on your wafer is warm. The latter can be done by blow dryer as suggested by Beachboy or pressing a hand over the bag for ~5 minutes after application. And as Beth said, your wafer cut should be snug but not tight. If it is tight against your stoma, it is not going to get a good seal and it will leak.
Are you using a flat wafer or a convex one? If your stoma is at all recessed, you should look at convex if you are using flat. Even if it is not, you may benefit from a convex wafer.
A little more information would be helpful. Do you have an ileostomy or colostomy? How long has it been since your surgery? What products have you tried? Are you using a stoma ring or stoma paste? There are many ways to get a good seal and not everyone is the same. Lucky ones like me can attach a flat wafer to dry bare skin and not worry about changing it for 4-5 days or even longer. I am able to stay away from things like adhesive spray or powders unless I have been careless with my seal and end up with a leak.
Success with a stoma can be like what I always told my kids about driving. Good habits make for good drivers. The same is true with an ostomy. :-)
Daniel