>>16485416>>1648554831 extra points in each stat can make a huge difference (even one point in HP can make a difference and you might survive an attack that would, without extra points, knock out your pokemon).
Getting good IVs takes a lot of time, I suggest checking this guide if you want to know about breeding IVs.
EVs are easily obtained in gen 6 since we have Super Training. There is even the graph that shows how much EVs you have in stats (use reset bag to start from the beginning with EVs).
