I post on my main site, here on Tapastic, and then I have an backup mirror on Tumblr. I also post pages early on Patreon, but it's not meant as a primary reading platform.
I prioritize my main site and Tapastic - and use those to point people towards my Patreon as well - because a.) having my own site is nice, as I'm in full control of its look and content, and b.) the Tapastic community is great. The tumblr is only there in case the other two decide to have hiccups.
If you want to use Tumblr, I recommend using relevant/popular hashtags, and to prioritize them properly - only the first five hashtags get indexed globally, so put the most important ones first.
But yeah, I don't really get a lot of attention on my dedicated comic tumblr - but I use my main art tumblr to point people to my website with teaser images every time I post a new page, and that seems to work alright!