Which Forum or Sub-Forum should I advertise in?

You were advertising in the correct area. It may be wise at attempting to improve your Title to grab attention more and improve your overall copy. You may want improve your offer in what you deliver and maybe test different pricing.

You could become more active in forum as well, and people will see your signature more and possibly click through and if they are interested in a writer. Make sure that the signature provides something catchy and compelling.

You're existing signature doesn't flow and doesn't really stick out.

Do you provide samples of your work in your WFH thread? Make sure you do that and to focus mainly on what you're best at and include that in the title. It appears you're trying to be all things.

If you want to continue doing different freelance work, I'd suggest you open a thread for each type of Job, such as Logo's, Articles. This way you can focus on that in Your Title and your copy. This can help grab the attention of people looking for something specific.

There is not a ton of traffic in the WFH forum but most of the time, people going there know Exactly what they are looking for.

Make sure that your offer is unbeatable compared to similar offers, whether it be the pricing, guarantee, extra, bulk deals, combination offers, or what have you.

Besides Warrior Forum ( I would stick with Warrior's for hire) I would check out all the outsourcing sites, one of my favorite ones is Elance. See whic one fits you best and develop a presence in the community -- it helps when people get to know who you are and have see you around for a while. ; )

Apart from the areas listed above, you need to start building your reputation. How do most, if not all, Warriors look at the member's reputation? They normally look onto the post count of the member and they take a look at the contributions of the member. Anyone can take a look at your previous posts. They can judge from there how you contribute to the forum. Highly-reputable members of Warrior Forum aren't here to just earn money. In most cases, it's a 50:50. You earn and teach others how to earn without spoon-feeding them.

Here people to do forum posting everyday and put link to your thread in the signature.

it's ok, i have been there too, take my sales thread in my signature for example, it's my third copy, and every time i learn something new,
first i offered free review copies, then offered a discount for bulk and for war room members, you can also try to offer discount for first 5 orders, and once the warriors here trust you and your quality work, the orders will flowwww
Best regards,
Alfred