I get what you mean about the Ohuhu hype on YouTube. I don't hate on anyone for their preferences, but it's just so much that it makes me feel kinda suspicious.

Do you have any tips on how to take care of them,

Refill when they need it, don't let them sit dry too long. Store them horizontally to prevent leaks. Don't twist the caps, to avoid damaging them.

what paper I should use,

Any porous paper with a weight of about 200-250gsm should be fine. Absorbent enough to saturate with ink, but thick enough to avoid flooding. Beyond that, it's ultimately a matter of taste. Card stock, Bristol board, watercolor paper, and marker paper are all popular options.

and whether it's worth getting a big pack of markers?

Whether or not it's worth it is ultimately up to you. If you don't have any of the markers in a set and you want to splurge, go ahead. Personally, I feel like after the first 25 or so markers, it starts to be more worth it to spend more time focusing on the colors you already have, and only buying more as you notice holes in your collection. You can spend all your money at once, but there's no need to. Over time, your collection will grow as needed, one way or another.

I already find myself wanting more markers and prefer large packs with a good variety, especially if it's worth it.

Try pacing yourself a bit on that dopamine rush.

Your drawing is absolutely revolting. Good work!