I have been on JP for 6 years now and am eagerly waiting to play on NA. Buying things is a chore, not only because of the language barrier but also the hoops you had to jump through to get US dollars converted to Yen, so I rarely ever did it. When I did put money into it (around $200 over the course of 6 years.. so around 30-35 bucks a year..) it was only for cosmetics. This game is TOTALLY viable to play without spending a dime. I never felt like I was behind other players. The cash shop in JP could be a bit of a trap however, buying certain convenience items was totally not worth the cost, while certain things like 30day Premium were a good value. So do some research if you ever decide to drop cash into the game. Otherwise, the game is pretty fun and complete without having to dump moolah into it. Much of everything loot wise is all RNG anyway, its not worth putting too much money into that mechanic.
Now I WILL acknowledge that the US version has a slightly different monetization model going on... Watching my brother play, he doesn't get as many freebies thrown at him as I do on the JP version, but the more rigid model doesn't rely AS heavily on gatcha games (aka lootboxes.) So only time will tell if they keep with the spirit of the game and do not use some kind of predatory tactic to change that feeling. I'm optimistic, but will be wary.