Upgrade cards with Credits to earn Collector Levels (CL). Every 120 CL earned gets you one Spotlight Cache, which is to say in that amount of levels you will get one Spotlight Cache and eleven Collectors Reserves. HOWEVER you should be saving any Reserves you earn now as the update isn't live (I think it is going to go into effect next season but not 100% sure.)
The reason is that when the update happens, you start earning Spotlight Caches based on your "first available" Reserve. So if you don't have any saved, you need to earn the full 120 CL, but if you have 12 Reserves saved by the time the update happens, one will transform into a Cache with the rollout and you can open right away.
The Caches will feature the new card each week, plus two featured series 4/5 cards and one random series 4/5 card. so all you have to do is save your Collectors Reserves for now and wait for a week with cards you want.