it is 95% strategy and 5% luck
i dont even know where to begin
lemme help you
practically the only mechanics in the game that are chance-oriented are:
successfully catching a pokemon
the slot machines in the Game Corners (the casinos)
the "run away" button for battles
the pokemon you will encounter when in tall grass
the underground wi-fi tunnels' mining minigames (diamond, pearl and platinum versions only I think)
the poffin/pokeblock machines when played with NPCs
the moves enemy NPCs will use in pokemon battles
the moves opponent pokemon will use in pokemon contests
the pokemon that spawn in a specific floor on dungeons (Mystery Dungeon games only)
the items at the lizard-carpet shops in dungeons and in Pokemon Square (Mystery Dungeon games only)
the chosen widescale movements of off-screen pokemon in dungeons (Mystery Dungeon games only)
the quests you can get from bulletin boards in pokemon square (Mystery Dungeon games only)
the terrain generation of dungeons (Mystery Dungeon games only)
also the pokemon are cute
which is a big plus
i dunno, some of the pokemon i have seen are creepy as Howard Wallowitz. That one pokemon that looked like a clown/housemaid was particularly scary