Why would they give you merit?
Because you write something worth giving merit to!
If you receive 2 merit, you'd have 1 sMerit (sendable merit).
This sMerit doesn't add to your merit, so it's only useful to give to other people.
So, therefore there's no reason for people not to give it away.
However, people only give merit to posts they think are good, or any criteria they prefer.
If you write good and/or informative posts, you likely will receive some merit at some point.
Looking at your recent posts, you're just posting in bounty threads, and the occasional sentence in other threads.
Tell me, why would anyone give you merit for that?
I have 12 merit, which isn't alot, but I've gotten mine only in the past few weeks from making threads and participating in discussions.
So, no, you don't have to buy any merit! And it's against the rules.
There's not really any guidelines on how you earn merit, as far as I'm aware.
If another person finds your post worthy, he might send you some merit.
So, start contributing with genuine posts, participate in discussions, maybe create some interesting threads, and I'm sure you'd receive some merit.
Posting on page 300 in an Altcoin Discussion thread with one sentence saying something generic isn't going to earn you any merit.
Again, anyone who receives merit, also gets half that merit amount as sMerit, which they can then give to someone, and it has no other purpose other than giving it to other people.
Final note, posting solely to earn merit I don't think is a good way to go about it, it's pretty obvious when people post only to receive merit.
Instead, start engaging in bitcointalk! There's this huge forum discussing all aspects of Bitcoin and crypto, I'm sure you find some aspect interesting.
Then engage yourself in that area! There's sections for technical discussions, general discussions, economy, and much more. There's even sections for discussions not related to crypto at all(such as Politics & Society).
There's an endless count of very interesting threads discussing all types of topics.
My suggestion is that you discuss with other users!
So, stop chasing merit, start engaging and contributing to the forum! Once you stop looking, it might come