If I got isekaid into my own fictional universe (technically haven't actually written it but whatevs) then that would mean that, according to it's rules, the reason I had knowledge about it beforehand could be for about, 3 different reasons? Two of which would definitely give me a distinct advantage. With that and my knowledge of the magic system, and with what I presume my elemental affinities are at, I'd be anywhere from decently well off to an immortal. So long as I don't get dumped anywhere too horrible, like in the middle of a war between the immortal races, a site of miasma apocalypse, or right in front of a matured, non-sapient Revenant. And I'd want to quickly figure out the exact details of how to program magecraft (magic circles n stuff) cause while sorcery would probably be enough to survive, setting up a mana gathering and storing array at a ley line nexus alongside some pre-made spells of mass destruction is op, at least when we're talking on a mortal scale. Otherwise, it's a decent kickstart to my development.