One problem is we already have ISS. But what we don't have is a gas station nor any platform in right orbit.

Question is, what is the right orbit?
51 inclination has advantage of allowing almost anyone to get to it. A zero inclination would have the advantage of lowest delta-v to get to if you launch from equator- but only Sea Launch launches at the equator- the French launch near the equator- 07 degrees. 28 degrees allows KSC to get to it, the French can get to it, and Russian can launch from French launch site [some of their rockets], but can't remember if Chinese have launch site at below 28 degrees- I don't think so, I believe it's 31 or 32.

Any of the 10 L-points would allow any launch site on Earth to get to it- though of course an Equator launch has lowest delta-v costs- but the other launch site don't need to pay an penalty in delta-v that is required to change their inclination.
Earth-Moon L-1 or 2 are the nearest L-points- and L-1 is the closest and is always in direct line of sight with all Earth each day [as it rotates]- and always has constant line-of-sight with Moon's Near side. All L-points basically have continuous sunlight and be good location to ship water from the Moon or other space water mining [such as NEOs]
The L-points are at high places in Earth's gravity well, fuel at the L-points would useful for final destinations such as the Moon or Mars. If you need fuel for GEO environment or if you need fuel to get from High Earth orbit to lower Earth orbit [if you want to get from Moon/Mars/high earth orbit to LEO- or if you want to lessen Earth's re-entry velocity].

But with all that said, the L-points probably aren't the best location to put up the first gas station, Low earth orbit is probably best location in the beginning. If space ports were private enterprise affairs, one value of gas station in a particular low earth orbit, would be a means of getting business for that Space port- it would be a value added to that launch location. Govt could of course have same purpose- though govt isn't as interested in lowering cost by increasing volume [though they like to pretend they interested in this] but govt places like KSC probably want to be the center that all the "business" for Manned Moon and Mars [more govt money and bigger bureaucracy].