Ready to run an ad campaign for my vocabulary app, where should I start?

A month ago I launched vocabulary app that lets users explore advanced english words, save ones they want to learn, and then teach themselves the words by taking simple multiple choice quizzes made from example sentences. The idea is that we learn words by seeing them in context, so there are about 100 example sentences per word allowing the user to get exposure to a bunch of different usages. It has about 400 downloads, most of which are friends and family + some people from reddit. I assume I probably won't ever make much money off this app, but I have seen the main Vocabulary app on the App Store have millions of downloads + saw on SensorTower that it generates about $200k per month in revenue. I actually began using this app when I was looking for what my app offers, but honestly was not impressed with the feature offerings. I'm assuming they probably have pretty high cost on marketing because I see them all over instagram and they come up as the first ad on the app store. Anyways, that makes me think that there is at least decent interest in the "vocabulary building" space and a potential to generate some revenue. This is also my first project and I spent a lot of time on it, so I'm willing to go a few grand in the hole to see if I can get a lot of downloads. If I do, then maybe I could throw some ads on the app or introduce a premium version and paywall some of the features. Idk. Anyways, would love to get advice on which direction to go. This is what I'm deciding between: 1. Instagram ads - tooting my own horn here but I think the app has a pretty solid looking UI, so I think the visual nature of instagram lends itself pretty well. Also instagram ads in general seem to be very effective (at least in my personal experience) 2. App store optimization - when I was looking for an app like this I just went to the app store and looked up vocabulary, but couldn't find what I was looking for. Maybe there are other people doing the same thing? 3. Reaching out to vocabulary / dictionary / productivity influencers I would prefer to only do one of these options and commit 1-2k over the course of a few months. But again I am a total noob to this so if anyone has insight would love to hear it.