Increase forum traffic for an established forum?

So i have a forum(xenforo) that's been online for around ~10 years, its doing ok, but i'd like to move up to the next step and just wondering hows best to increase traffic?

I've done some SEO, but still learning, if you search in google/bing/etc for "my niche forum", it is the top result, i have social media accounts (fb page and twitter) but only really use for auto posting from the forum, also its not really the type of audience where a monthly giveaway, or competition would really…

Increase forum traffic for an established forum?