what would be a solid sample size to hit before one can determine if they're ready to move up in stakes, assuming i also have the bankroll to move up?

i'm thinking 250-300 games with a solid 10-20+% roi would be good. is that overkill or maybe too low?

With MTTs variance is so large, that you need a sample of 1.000s to get near your true long term ROI. And during that time hopefully your game has evolved, and maybe the player pool has evolved as well. So you are kind of shooting at a moving target, and if you want "confirmation" from each level before even dipping your feet into the next, you probably end up unnessesarely limiting yourself.

So with MTTs I just basically follow the 1% rule and never (or at least rarely) buy in for more than 1% of my bankroll. Its also not desirable for me to play just one limit at a time, since then I would never get any volume. So in reality I always play a fairly wide spread of buyins having for instance a 3,3$ MTT and a 12$ MTT running in the same session. This also prevents me from "moving up to fast", since my schedule still contain a lot of the games, I was already familiar with.

The only reason I can see to deviate from this would be, if you binked a very large score maybe as part of a reward program or something, so that your bankroll shot up multifold due to this single win. Then I would not move directly from 5$ to 50$ MTTs but rather withdraw the bulk of those money and spend them on something else.

But if your bankroll has grown from 500$ to 3.000$ due to many small or medium sizes cashes in tournaments, that were within your bankroll, then I dont see any reason, why you should not try some 30$ tournaments, just because you have not yet played a random number of 12$ tournaments.

Also simply look at if the games are good. If there are recreational players at the tables, then you are probably going to be profitable, if you are a solid player with a proven track record. Whereas if the opposite is the case, then maybe not so much. And then maybe there is not even any point in moving up. Unless maybe if you are specifically looking for the excitement of playing for bigger money, or to challenge yourself by facing better opponents. I hope this explanation was helpfull