Your best chance of quickly turning 25$ into a small bankroll is to play
roulette and put all your money on either red or black. If you win 2 times in a row, then 25$ has become 100$, and it takes less than a minute. Of course 3 out of 4 times you will go broke, but this will also happen, if you try to turn 25$ into 100$ playing 3,3$ MTTs.
A reasonable starting bankroll for the 2,2-3,3$ MTTs on PokerStars is 500$. With anything less than 500$ you should begin in the SnG section. 25$ is enough for the 25c 45-90 mans. Its possible to grind it up from there, but its going to take a very long time. Of course if you are just playing for fun, then do whatever you want. 25$ is enough to play 10 of the 3,3$ PKOs, if you win at least something like a few bounties. And then you can just deposit again, when the money is gone, and you still want to play.