john18061806I was planning on buying ISO 400 fujifilm but a better question would be what to avoid. I've learned that being naive is the downfall of any investment. Even a microscopic one like a roll of film. I've wasted my money on a lot of music equipment due to incompatibility and poor quality, it's just a terrible feeling knowing that you could've put your money to better use.
You can't go wrong with glorious Tri-X or many films in general. But they all have their own learning curve and benefits.
I'd say for the first few rolls get some cheap colour Fuji 200/400, they can be developed in C-41 which most places can do for a few bucks, just enjoy the process, you will make mistakes but it's better if it happens on a 2 buck roll of Fuji Superia.
If you want black and white: Tri-X or it's brother from another mother: Ilford HP5. B&W is usually more expensive to get processed but easier done yourself then C-41. Those two films are loved because of the sexy grain, hard contrast and ridiculous ability to be shot at ISO 25-12800 with ease (do note that pushing/pulling that far requires some developing magic). Also it's reasonably cheap and easy to get hold off.
Other films are for the future and by then you will know.
Don't buy Velvia or other films that have little exposure latitude, or strange low iso panchromatic films that perish if they aren't developed within a day after exposure, then again these films are also usually priced higher and thus easy to spot.