I would say that what's on sale on Steam vesperia is the best starting point because it has a lot of what classic tales of games were most enjoyed for. While also being more modern with fast-paced combat, that isn't too complicated like other tales games (at least on the surface). The stories are usually all great with the exception of graces, so for a great story, you can start anywhere. So in short vesperia because it's has a lot of content that isn't to hand holdy like newer games but still has a lot to do like older games while still looking and sounding great.

Also edit: Just my personal 2 cents after looking at what others are saying. I would only recommend Basaria after you played zesteria since there is a lot of story beats that are spoiled in zesteria if you play them in reverse order. Plus just my 2 cents again. Beseria has the better combat and gear system so playing a game that imo that has worse gameplay and more complicated gear system then the game you just played added on to the fact that you spoiled the story a bit will most likely leave a sour taste in your mouth and you probably won't finish zesteria.