As stated above, posting packages is a great way to get the beginning content you need to make your forum look not as dead. Users tend to go with a site that looks active, and ignore those that are not. This is a good trick for the beginning, and to get some content on your site. While this is going on, make sure to post and stay active as well on the posts whilst making open ended, and discussion friendly posts. I made an article here
https://www.webmaster.college/posts/695/ (Sorry if this is self advertising, feel free to remove the link however I feel it is here specifically to help the user out). This article explains how important it is to make the right topics/posts based on your forum.
Once again, as stated, make sure you go on other bigger forums, and have your site linked somewhere, either signature if allowed, or on your profile. Don't just make posts, make acquaintances, friends, and build bonds. Remember that you're on this to eventually represent your website, and gain the individual users trust. This way you will have more of a following, and people that are more willing to join your site. Of course, through posting on the site with your signature link you will get more members and views of your site. Though through the time of building bonds, and friendships you will more than likely have a higher word of mouth growth.
Promoting your site on other sites will be helpful. Sites like ForumPromotion is a good way to at least get your sites name out there. Some people may be interested in your niche, and join it.
Reddit is also another great way to gain views/members. Someone mentioned an anime site, so I'll use this as an example. If you make an article on something anime related that is good, high quality, and post it on reddit in the proper subcategory you can get a lot of views. I've gained over 100 members at one time off of a single reddit post. Most people over look Reddit, and other sites like it as a way to advertise. As long as you're active on reddit, and make a 1 link to 10 post ratio you tend to be pretty good.
If you're interested in investing money into your site, you can message users of bigger sites in your niche, and try paying them to advertise your site. This is something that will bring in a lot of users assuming the user wishes to have your site advertised. I've contacted several people about multiple sites of mine, it's really a 50/50 depending on. Some people want the money, others don't want the competition advertised on their website. However, this a perfect way if accepted to gain members and activity.
A site will never get big overnight, it will take a lot of hard work and dedication to get your site active, especially a dead website. I am unsure why, but I find it harder to revive a dead website than a new website. I think it might be the stigma behind the site possibly dying again.
I hope this helps out even a little. If so, I'm really glad, if not I am sorry for wasting your time with this overly long post.