Steam Event 2019 someone explain me?

https://www.steamgifts.com/discussion/B8B73/grand-prix-explained-simple

for coins you need capacity, you get 121 capacity for each 1eur/usd you spend on steam store and you get some free each day.

You need points only to use these capacity value.

You dont need to earn new achievements, just idle any game during the sale for 30mins where you earned achievements in the past and you can claim points for those earned achievements. BUT: You can claim points only if you have unused capacity and your point value not enough for it.