I'm not sure what you mean by the panel system -- that might be photosets? Can you explain what's confusing you?
Tumblr has a couple of uses! A lot of people are on tumblr, so it can be a useful social media to stay connected to your audience -- posting art, answering questions, reblogging things you like, etc. For folk who use tumblr casually it can be a way for the people who follow your art to get to know you better.
But if you're looking to be discovered on tumblr, in my experience people find new blogs they're interested in (a) from someone they follow reblogging it or (b) from the tags, which is the answer to your second question -- if I draw Undertale fanart, and tag it "#undertale," then it shows up in the Undertale tag, and people looking for Undertale fanart will see it there. Only the first five tags you use will work this way (the rest are just to organise your blog) so it's good to be thoughtful of your first five!
It might help you to find other artists who do the kind of art you do, or draw subjects you're interested in, and see what tags they're using on their work? Or, search tumblr for tags that you think might describe your work, and see if you can find that sort of thing posted there, and what other tags those posts use!
I feel like the easiest way to find new people is honestly to be part of a community there. For a lot of us, that's gonna be fandom -- draw good fanart and tag it appropriately and that fandom will find you. And if you post often, a small percentage of the people who follow you for your fanart might be interested in your official stuff as well!
Tumblr, in my experience, can feel like yelling into a void for a while, though. It took me at least a year (and some Homestuck fanart and reblogs from friends) before I had enough of a following there to feel like anyone was responding to the things I posted. But I guess, I was never really using tumblr solely as a promotional tool? For me it started out as a place to be more casual and share silly fanart and sketches of my friends' D&D characters. And some of that stuff has found me an audience on tumblr, and a small percentage of that audience is interested enough in my original work to like it and share it with others.
I like tumblr okay! But I don't know how useful or efficient it is if you're solely using it to promote.