Lol dude I was in bronze for ages and picking up my 1 card and then suddenly hit silver and gold pretty quickly like in the space of 3 days I went from bronze to gold with the same cards. No upgrades and I literally just play for the daily quest and then move on with my day. I do have 33 monsters that are level 3 and up but only 1 level 3 summoner so it doesn't help much