>>28263212shufflemove is a program that calculates the best possible move in a certain situation and is very helpful to get good 5+ combos
psb = personalized skill booster. Basically improves the ability of a pokemon.
In shaymins case it increases the chance of sleep charm triggering.
LV1 (0psb): 5% on a 3match, 30% on a 4match, 80% on a 5match
LV2 (1-5psb): 15%, 40%, 90%
LV3 (6-20psb): 20%, 45%, 95%
LV4 (21-40psb): 23%, 48%, 98%
LV5 (41-100psb): 30%, 55%, 100%
Sleep charm is one of the best abilites in the game as it puts the pokemon to sleep and so it wont disrupt for 3 turns. Also damage gets increased. And shaymin being grass type is SE against water and ground and can put them to sleep (a few types are immun to sleep like dragon). Also if we count all pokemon still to get released, there are over 30 being water or ground. So you have the chance to use shaymin a lot.
Thats why you should absolutely make sure to catch the small fucker and grind him up to lv 3 at least. You grind his ability by playing the stage again after you caught it. The chance to get a PSB is around 30-40%. So you gotta play the stage a few times.
also dont bother to get mewtwo if you dont have time right now, as this will cost some time/effort. In this case use M-Gengar and Pokemon with the ability quirky (like xerneas). Also shufflemove and make sure to have a 3+ combo each turn so sunday meowth disrupts with coins.
tl;dr: gid gud