has anyone spent any money on this? is anything worth it?
I may have spent some... money on it in the last 2 years yes *cough*
Recommending specific weapons to buy is difficult as it depends on your play style. I'd only consider buying weapons that would otherwise cost 1000 certs though.
I'd say if you see yourself playing regularly, joining an outfit and sticking with the game for a period of time then membership would probably be the most worthwhile. You get more xp, more resources, 500 station cash a month and priority in queues between continents. Combine that with an xp boost and you'll be getting plenty of certs if you play reasonably effectively.
Remember the only things that cannot be unlocked with just certs (1 earned for every 250xp) are cosmetic items (helmets, armour, camo, decals, lumifiber etc). Any weapon other than silly golden variants can be unlocked with certs. So you can either save some time and buy it with money, buy membership and/or xp boosts to earn those certs faster, or just play for free and unlock it when you get there.
If you like NS weapons (NS-7 PDW, Commisioner, Bursters for the MAX, NS-11A, C etc) then they're a good choice to buy with station cash as they can be used across all empires.
Also, if you do see yourself playing for a while they'll likely have a sale around Christmas and possibly Black Friday, last year they had things like 50% off an entire category (e.g. vehicle weapons) each day plus an item for sale at 1 station cash each day. So you could get say membership now, save up the 500 per month and have about 2000 station cash and pick up a bunch of things then.