I've had an Ileostomy for 15 years. I carry a fanny pack with:
1. a collapsible water bottle. Platypus makes a good one and Amazon carries some cheaper Chinese made ones. It's for cleaning the pouch when you have to empty away from home.
2. A spare pouch and the usual supplies needed for a change in case of a major leak. Major leaks are rare but they do happen.

As far as irritation around the stoma I would start by trying as many different pouches as you can. Most pouch manufacturers will send you free samples. Everyone is different and you have to find what's best for you. I ended up using a Coloplast Mio Deep Convex but Convatec and Hollister also were good. Search online for Ostomy pouch manufacturers and get as many samples as you can.

As others have pointed out stomahesive powder helps protect the skin. I prefer to use a pump spray protective barrier rather than a wipe