Some achievements will give you cartel coins but not that many of them. About 20 and thats only some achievements. Alternatively if you subscribe you get about 500 a month, or if you set up a security key you can get 100 a month. Also if you subscribe you can use a referral link to get 600 coins if someone who is subscribed clicks on it. There are some forums where you can post your referral link or you can put it in your signature or post. Also you can Offer people credits in game to click on your link. It is perfectly fine to do that and does not break any rules