It depends how hot you like your vapor. 1.5s or 1.7 are good on the mini if you like hot/warmer vapor, 2.0 if you like it cooler. Anything too much above that and it gets too wimpy at 3.7 volts. You won't damage the mini unless you go below perhaps 1.0 or the atty shorts.
510 and 306 attys work well, just make sure you get a good appropriate drip tip to go with them. Cherry
vape Universal works with both, Cannons are fabulous with the 306s, pawns and mings with the 510s. Any delrin drip usually works well too if you are on a budget. If you get 306 attys and drip tips, look for the long or XL versions to avoid getting
juice splashes in your mouth.
Don't panic, try the cartos to see if you like them before you start ordering new stuff. If they are too hot you know to go higher in an atty, if too cool then a 1.5 306 atty might be more appropriate. Baby steps.
Enjoy your mini.