I advice you to buy the Iso wisely If you invest on character that can farm Iso fast ( as in Tournament or shield training) then do so if not then don’t. Read on my How much ISO can you collect a day topic https://forums.505go.com/discussion/289
I’d rather buy HP. I’ve bout 30k ISO saved up from about 2 weeks of playing naturally (I prefer keeping my character levels as low as possible). Do the PVP tournaments. That’s where I get most of mine.
If you do decide to spend money to get HP, make sure you know what you want to do with it before you buy. I wouldn’t put much into gambling random packs.. any HP I get now is gonna be for leveling skills