From the moment you open Planetside 2 until one day you uninstall, your ears will ring with the siren call of "Certs..." the magical currency in PS2 that makes Auraxis go-round. From the get-go you begin amassing certs to purchase everything from upgrades to new capabilities. It costs 10 certs to learn to use an Auraxian toilet. I wouldn't be surprised if eventually it costs 100 just to be able to logout. Certs are gained primarily through earning experience; so killing, maiming, reviving, assisting, hacking, capturing, rearming, sunbathing...basically everything you do in PS2 aside from breathing (costs 20 certs) earns you xp which earns you certs.
Many classes and vehicles start out "nerfed" in some manner, requiring either certs or station cash to "un-nerf" them. Much like EVE after several years, soon enough playing PS2 for a new player will be less about opening up variety, and more about "un-nerfing" yourself relative to other players. Whereas in Planetside 1, the point of certs was to offer versatility, in PS2 you already have access to all the vehicles and classes, so certs become about "specialization" (which is an industry buzz-word for "grinding like hell so that you can be as good as everyone else at a role").
"But Clockwork, the weapons are all side-grades and the cert bought upgrades are all small."
My friend, let me take that cup of Kool-aid from you for a moment. Go look at the weapons again; is your fare the sniper? Then start saving up for a 1000 cert bolt-action that does more damage with higher projectile speed than any other. "But it reloads slowly!" Oh I forgot how important reload speed was to a sniper when using a head-shot killing rifle, my mistake. Find me a few credible snipers that would prefer a slightly faster reload speed to a better chance of a kill in a shot, and I'll eat my hat*. Are you more of a heavy assault? Well if you are Vanu, I hope you enjoy LMGs with 50 round magazines that empty faster than a teenager who just discovered the internet. Or you could spend 1000 certs once more for a rifle with slower rate of fire, higher damage, and 50% more ammunition.
Maybe you prefer to pilot? Well your Liberator comes standard with a chain gun that can tear through a tank in 3 magazines! Your Empire Specific Fighter (ESF) comes with a stock machine gun and extra afterburner fuel pods. Those will be handy for running away, or spending 3 minutes shooting at a ground vehicle in hopes of a kill. Where "side-grade" anti-air missiles are only 500 certs away, or rocket pods at 1000....
Hopefully the point is clear but I could cite examples of the Lightning, empire specific tanks...
As for upgrades, for a few hundred certs you can have 50% more HP, assured survival against certain attacks and a clear advantage against someone without. Or you could have 50% resistance to explosions; letting you laugh away the mines or grenades of other infantry...or survive a tank's shelling.
The importance of Certs leads to experience efficiency being paramount...anything to get your next few a little faster. For example, I have watched people destroy FRIENDLY Sunderers so that they could deploy their own to get the experience. Being a tanker or ESF is vastly more entertaining than infantry because it's a safer means of getting that xp. Despite holding to my "do what's fun" mantra, even I have found myself tugged towards the rocks of less-fun by the siren call of faster xp.
I hope they improve things, at this rate "unnerfing" yourself is going to just become more an more of a chore; and if you aren't ahead of the curve, then the average player will be better equipped than you.
* Hat may or may not be substituted for cake.