I've had a pretty decent run putting my stuff on Archive of Our Own. The tagging system is a lifesaver for a series like Dragon Ball Super, because you can filter for 'Original Characters' or 'OC-Centric' and actually find an audience looking for that specifically. The search is granular enough that people who want Goku/Vegeta won't stumble into your OC-focused saga and leave grumpy comments.
That said, it's not an instant audience. You have to be patient and tag well—'Dragon Ball Super', 'Original Characters', maybe 'Adventure', 'Action', maybe even 'Canon-Typical Violence'. It helps to tie your OC into the existing world in a believable way; I wrote a series about a scientist from Universe 6 studying God Ki, and it attracted readers who were into the lore side of things. FF.net also works, but the interface feels older and it's harder to stand out unless you update frequently.
Wattpad is a different beast. The culture there skews younger and the algorithm favors certain tropes, like romance between an OC and a canon character. If your story has that element, it might gain traction faster, but the feedback can be less detail-oriented. I cross-post to Ao3 and Wattpad just to see the different reactions, which is kind of fascinating in itself. The key is to finish your first arc before you post anywhere—DBS fans can be harsh if you abandon a premise.