What has worked for us is to just go with bare bottom or use regular panties and set the "peepee bell" for every 15-20 minutes in the beginning of training. If you are going to potty train you have to ditch the diapers except for outings, nap and nighttime. I never made the connection with my kids that diapers=baby so we never had problems switching back and forth.
My 25 month old has been interested and training since she was 17 months old. We never use diapers except for the above situations. And there are times when we are out that she stays dry so I'm encouraged! Just harder for her to remember all the time when we are out and busy.
You could always put a regular diaper cover on over the panties if you want to avoid a mess. But them feeling the sensation and making that connection really made a huge difference with mine. And yes, there were messes for the first week then it improved. Wasn't perfect of course but it improved.
I didn't see any reason to buy the training pants when I already had covers and pocket diapers(without stuffing) that I could use as protection. But I never used them at home with training.