the station i was at before the DLC dropped had a G3 Dominator suit, was about 3M credits iirc. but none of the other suits and only Plasma and laser weapons no kinetic so it's scattered across the galaxy.
i think G3 will be the highest you can buy.
but some content creator's will let's us know eventually.
G3 should be more then enough to complete most PVE content, PVP or CZ can grind G4 much quicker, now you have the choice.
if you can "skip" G1 & G2 and get a "Clean" G3 which can still be upgraded and attachments added later, why not?
the thing that bothered me the most about the "Alpha" was the insane amount of time it took to get the unique items needed for upgrades, without the ability to exchange like we have with ship engineering. i NEVER found a single power regulator the entire time.