I cant buy it too expensive.

Take your sP to buy CSC by playing games, restocking, doing quests.

I was hoping there was a cheaper way then using my sP

There isn't unless you use your real money. You can also try to participate in giveaways from other users.

If you come by particularly expensive items, you can put them up in the trades and ask for their worth in CSC. You can also create custom wearables, for which you get a royalty. You also get 5% (or is it 10?) of all CSC spent by users that you invite to the site. There is also an achievement prize for connecting your Subeta account to your Facebook account, which is 100 CSC. Otherwise, buying CSC gift cards with sp is your best bet. P.S. it's easier to motivate yourself if you have something specific to save up for. Good luck!