TLDR: if you want to be competitive, dont bother unless you live in the middle of a city and dont have a day job; if you want to have fun, uninstall this game and play the console Pokémon games that youd really rather be playing, anyway.
I really wanted to like this game; Pokémon games made my childhood - but the way Pokémon Go was designed, if you dont live in a densely populated area, just give up because you will not be able to have anything remotely resembling a pleasant gaming experience.
Pokestops and Gyms are the entire game. Sure, itd be great to go off and do your own thing, walking the distance and occasionally catching something, but without pokestops, you will run out of pokeballs drastically faster than they can be replenished unless (again) you live in a very densely populated area. Likewise, you cant hope to enjoy the gym scene unless you have a large supply of medical items at your disposal which you can (AGAIN) only get from pokestops.
The release of legendaries makes this problem even worse; with minimum suggested raid sizes of 20 to even be able to defeat a legendary (dont even think about trying to catch one), its impossible unless you live in a very densely populated area (or just happens to have a group of 20 eager friends willing to meet up and battle a gym after work). On top of that, with the availability of legendaries being limited to a short time window, if you miss it (because you dont live in a city and have the flexibility to be available during peak foot traffic times), youre permanently out of luck. This ultimately limits legendary attainment to those who can afford the time and resources to travel to a major event area (like Chicago during the anniversary), and because they are so much more powerful than standardly-obtainable Pokémon, this limits competitiveness to a very small select few (articuno alone is a giant counter to just about every pseudo-legendary which are primarily dragon-types).
Long story short: if you want to be competitive, dont bother unless you live in the middle of a city and dont have a day job; if you want to have fun, uninstall this game and play the console Pokémon games that youd really rather be playing, anyway.