Bro, I don't think many will subscribe to a series they probably won't be able to read, most of the people in the Forum speak English, and the mayority of the userbase in the platform/app itself are mostly english speakers too.
Spanish, Portuguese and other languages don't do as well in Tapas, even more when they are Independent or from small authors. So, my recommendation is to try to promote yourself in brazilian or portuguese communities so at least you can gain some genuine readers.
Otherwise the only way you may get subs its if you publish your series in English, so the mayority of the userbase can be able to read it.
Still, sub x sub is quite meaningless thing to do because its just inflating a number but there won't be real engagement to your series, not actual commited readers, nor comments or likes. As well, many will subscribe to you just so you do it back, but after a few days they'll unsub or just totally ignore your series.
