Personally, I don't recommend this one (which is FF1). It's a very old, fairly simple game. The characters and story aren't much at all. It's not like it's bad in a vacuum, but there's simply better games you can play, especially to start with.
FF10 is perhaps my favourite and a very popular fan favourite. If you want something a bit older (which can be useful for mobile support), FF6 is hands down the most popular of the 2D Final Fantasy games (and some would call it the best FF game).
Pretty much all the older main series games have been remastered in some form or another, some multiple times, and are available at a fair price. Most are available on PC and several have mobile versions (plus the older games emulate very well).