You don't need to keep creating threads, and if you're out of ideas, bitcointalk is probably not for you. Oh wait, you're here to earn money and feel pressured to keep writing stuff.
If you don't have anything new, don't start threads--it's that simple. The forum will be just fine if you just sit back and read, believe me.
Yes, and after reading, sometimes you will come up with ideas to reply to posts. You can be merited for your comments as well, although you are more likely to get merits, and to get more merits, if you create good post.
But it is better as @The Pharmacist says that you use the forum as a source of infomation, to try to find some good posts to read, and ideas will come up, either to comment or to create new posts. Don't be in a hurry.