Welcome! As you probably cannot help but be aware, Dreamwidth began as a fork of Livejournal, and its interface and features largely hail from an older time. The codebase is old enough to vote. Interacting with people and keeping an active blog on Tumblr is really low-effort in a way that it isn't necessarily on Dreamwidth, so I thought I'd post some pointers for translating the way you interact on Tumblr over to Dreamwidth.
- Dreamwidth does not have likes, but it's totally acceptable to comment on a post to communicate the same basic thing. Same with comments, or you can just say "+1" [EDIT: If you used your likes more like bookmarks, you might be interested in the memories feature.]
- Notice how you have 15 icon slots (more if you have a paid account?) In comments, you can use your choice of icon like a reaction gif. (You can, of course, also post a reaction gif in the body of your comment.)
- There are two very different ways of responding to someone's post. One is to reply and discuss the post with the original author. Another is to use the original post as a jumping-off point for a substantial post of your own. On Tumblr, you would generally use a reblog for either of these types of response. On Dreamwidth, you usually want to use comments to reply/discuss, but if you're using someone else's post as a springboard, you should instead make a post of your own and link back. You might also post a link to encourage your subscribers to get involved in the discussion on the original post. Linking and commenting are pretty core to how people find each other.
- Ask memes! Dreamwidth doesn't have asks, obviously. Instead, you would make a post for the meme list of questions, your subscribers would comment with the questions they'd like you to answer, and you might reply to that comment or in a follow-up post, depending on length/substance/personal preference.
- The linkspam is a classic LiveJournal Post Type with a venerable history. A post can just be a link or handful of links to stuff that you liked or thought was interesting. A post can also just be a list of brief updates/thoughts on what's going on in your life that might not all constitute a "post" on their own.
I hope this is helpful - it's been a while since I was particularly active, but I've been on DW for a reasonably long time (longer than just this account), and if you have any questions I can probably help you find answers.
(also, a major quality of life tip: you know how it takes you to a completely new page when you want to subscribe/grant access to someone? Yeah, you can actually skip that - if you hover over the little icon next to someone's name, there's a popup you can use to subscribe/grant access without navigating away.)