Time for my math skills.
Umm...212 subs and we posted the first page August 23rd ...so 8 days of August, 30 days of September, 15 days of October = 53 days... maybe around 4 a day?
But yes, get busy with social media, especially if you don't have a big following already. I recommend Reddit and Facebook boosts mostly, just remember what specific audience you want to reach, find some really cool ad ideas that will attract folks, and watch your spending. Yeah, I said spending. Unfortunately you're going to have to do at least a little bit. To reach about 500 people on Facebook, for example, with a targeted audience, you'll have to spend about $3 per day. Facebook recommends at least a 4-day run to be successful, but we did okay with 3.
I'd also recommend Twitter. It can be very effective, and again you can budget this out for impressions and engagements. But if money is really tight, and understandably so, it costs virtually nothing to create cool 3x5 brochure cards and hand them out at comic shops in your area. MOST comic shops will definitely help your marketing plans - especially if you buy a few comics from them in return. Look over the $1.00 bin (every comic shop has one, I imagine), and root around for some classics, and you can usually, with permission, set a small stack of cards on their counter.
Hope this is helpful. there's other ways to promote too, but see what you can do with these first.